Governance docs per CE PR 1226

Signed-off-by: Doug Davis <dug@microsoft.com>

CONTRIBUTING.md

@@ -0,0 +1,167 @@
+# Contributing to CloudEvents' PHP SDK
+
+:+1::tada: First off, thanks for taking the time to contribute! :tada::+1:
+
+We welcome contributions from the community! Please take some time to become
+acquainted with the process before submitting a pull request. There are just
+a few things to keep in mind.
+
+# Pull Requests
+
+Typically, a pull request should relate to an existing issue. If you have
+found a bug, want to add an improvement, or suggest an API change, please
+create an issue before proceeding with a pull request. For very minor changes
+such as typos in the documentation this isn't really necessary.
+
+## Pull Request Guidelines
+
+Here you will find step by step guidance for creating, submitting and updating
+a pull request in this repository. We hope it will help you have an easy time
+managing your work and a positive, satisfying experience when contributing
+your code. Thanks for getting involved! :rocket:
+
+* [Getting Started](#getting-started)
+* [Branches](#branches)
+* [Commit Messages](#commit-messages)
+* [Staying current with main](#staying-current-with-main)
+* [Submitting and Updating a Pull Request](#submitting-and-updating-a-pull-request)
+* [Congratulations!](#congratulations)
+
+## Getting Started
+
+When creating a pull request, first fork this repository and clone it to your
+local development environment. Then add this repository as the upstream.
+
+```console
+git clone https://github.com/mygithuborg/sdk-php.git
+cd sdk-php
+git remote add upstream https://github.com/cloudevents/sdk-php.git
+```
+
+## Branches
+
+The first thing you'll need to do is create a branch for your work.
+If you are submitting a pull request that fixes or relates to an existing
+GitHub issue, you can use the issue number in your branch name to keep things
+organized.
+
+```console
+git fetch upstream
+git reset --hard upstream/main
+git checkout FETCH_HEAD
+git checkout -b 48-fix-http-agent-error
+```
+
+## Commit Messages
+
+Please follow the
+[Conventional Commits specification](https://www.conventionalcommits.org/en/v1.0.0/#summary).
+The first line of your commit should be prefixed with a type, be a single
+sentence with no period, and succinctly indicate what this commit changes.
+
+All commit message lines should be kept to fewer than 80 characters if possible.
+
+An example of a good commit message.
+
+```log
+docs: remove 0.1, 0.2 spec support from README
+```
+
+### Signing your commits
+
+Each commit must be signed. Use the `--signoff` flag for your commits.
+
+```console
+git commit --signoff
+```
+
+This will add a line to every git commit message:
+
+    Signed-off-by: Joe Smith <joe.smith@email.com>
+
+Use your real name (sorry, no pseudonyms or anonymous contributions.)
+
+The sign-off is a signature line at the end of your commit message. Your
+signature certifies that you wrote the patch or otherwise have the right to pass
+it on as open-source code. See [developercertificate.org](http://developercertificate.org/)
+for the full text of the certification.
+
+Be sure to have your `user.name` and `user.email` set in your git config.
+If your git config information is set properly then viewing the `git log`
+information for your commit will look something like this:
+
+```
+Author: Joe Smith <joe.smith@email.com>
+Date:   Thu Feb 2 11:41:15 2018 -0800
+
+    Update README
+
+    Signed-off-by: Joe Smith <joe.smith@email.com>
+```
+
+Notice the `Author` and `Signed-off-by` lines match. If they don't your PR will
+be rejected by the automated DCO check.
+
+## Staying Current with `main`
+
+As you are working on your branch, changes may happen on `main`. Before
+submitting your pull request, be sure that your branch has been updated
+with the latest commits.
+
+```console
+git fetch upstream
+git rebase upstream/main
+```
+
+This may cause conflicts if the files you are changing on your branch are
+also changed on main. Error messages from `git` will indicate if conflicts
+exist and what files need attention. Resolve the conflicts in each file, then
+continue with the rebase with `git rebase --continue`.
+
+
+If you've already pushed some changes to your `origin` fork, you'll
+need to force push these changes.
+
+```console
+git push -f origin 48-fix-http-agent-error
+```
+
+## Submitting and Updating Your Pull Request
+
+Before submitting a pull request, you should make sure that all of the tests
+successfully pass.
+
+Once you have sent your pull request, `main` may continue to evolve
+before your pull request has landed. If there are any commits on `main`
+that conflict with your changes, you may need to update your branch with
+these changes before the pull request can land. Resolve conflicts the same
+way as before.
+
+```console
+git fetch upstream
+git rebase upstream/main
+# fix any potential conflicts
+git push -f origin 48-fix-http-agent-error
+```
+
+This will cause the pull request to be updated with your changes, and
+CI will rerun.
+
+A maintainer may ask you to make changes to your pull request. Sometimes these
+changes are minor and shouldn't appear in the commit log. For example, you may
+have a typo in one of your code comments that should be fixed before merge.
+You can prevent this from adding noise to the commit log with an interactive
+rebase. See the [git documentation](https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History)
+for details.
+
+```console
+git commit -m "fixup: fix typo"
+git rebase -i upstream/main # follow git instructions
+```
+
+Once you have rebased your commits, you can force push to your fork as before.
+
+## Congratulations!
+
+Congratulations! You've done it! We really appreciate the time and energy
+you've given to the project. Thank you.

MAINTAINERS.md

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+# Maintainers
+
+Current active maintainers of this SDK:
+
+- [John Laswell](https://github.com/jlaswell)

README.md

@@ -117,3 +117,10 @@ how SDK projects are
 for how PR reviews and approval, and our
 [Code of Conduct](https://github.com/cncf/foundation/blob/main/code-of-conduct.md)
 information.
+
+## Additional SDK Resources
+
+- [List of current active maintainers](MAINTAINERS.md)
+- [How to contribute to the project](CONTRIBUTING.md)
+- [SDK's License](LICENSE)
+- [SDK's Release process](RELEASING.md)

RELEASING.md

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+To create a new release:
+- Create a new Github release via the Github UI, making sure to prefix it
+  with `v`