docs: Update README to match OpenFeature template (#147)

Signed-off-by: Max VelDink <maxveldink@gmail.com>

CONTRIBUTING.MD

@@ -0,0 +1,98 @@
+# Contributing to the OpenFeature project
+
+## Development
+
+You can contribute to this project from a Windows, macOS or Linux machine.
+
+On all platforms, the minimum requirements are:
+
+* Git client and command line tools.
+* Ruby 3.0 or higher
+
+## Pull Request
+
+All contributions to the OpenFeature project are welcome via GitHub pull requests.
+
+To create a new PR, you will need to first fork the GitHub repository and clone upstream.
+
+```bash
+git clone https://github.com/open-feature/ruby-sdk.git openfeature-ruby-sdk
+```
+
+Navigate to the repository folder
+```bash
+cd openfeature-ruby-sdk
+```
+
+Add your fork as an origin
+```bash
+git remote add fork https://github.com/YOUR_GITHUB_USERNAME/ruby-sdk.git
+```
+
+To start working on a new feature or bugfix, create a new branch and start working on it.
+
+```bash
+git checkout -b feat/NAME_OF_FEATURE
+# Make your changes
+git commit
+git push fork feat/NAME_OF_FEATURE
+```
+
+Open a pull request against the main ruby-sdk repository.
+
+### Running checks locally
+
+#### Unit tests
+
+To run unit tests and other checks:
+
+```bash
+bundle exec rake
+```
+
+### How to Receive Comments
+
+* If the PR is not ready for review, please mark it as
+  [`draft`](https://github.blog/2019-02-14-introducing-draft-pull-requests/).
+* Make sure all required CI checks are clear.
+* Submit small, focused PRs addressing a single concern/issue.
+* Make sure the PR title reflects the contribution.
+* Write a summary that helps understand the change.
+* Include usage examples in the summary, where applicable.
+
+### How to Get PRs Merged
+
+A PR is considered to be **ready to merge** when:
+
+* Major feedbacks are resolved.
+* It has been open for review for at least one working day. This gives people
+  reasonable time to review.
+* Trivial change (typo, cosmetic, doc, etc.) doesn't have to wait for one day.
+* Urgent fix can take exception as long as it has been actively communicated.
+
+Any Maintainer can merge the PR once it is **ready to merge**. Note, that some
+PRs may not be merged immediately if the repo is in the process of a release and
+the maintainers decided to defer the PR to the next release train.
+
+If a PR has been stuck (e.g. there are lots of debates and people couldn't agree
+on each other), the owner should try to get people aligned by:
+
+* Consolidating the perspectives and putting a summary in the PR. It is
+  recommended to add a link into the PR description, which points to a comment
+  with a summary in the PR conversation.
+* Tagging subdomain experts (by looking at the change history) in the PR asking
+  for suggestion.
+* Reaching out to more people on the [CNCF OpenFeature Slack channel](https://cloud-native.slack.com/archives/C0344AANLA1).
+* Stepping back to see if it makes sense to narrow down the scope of the PR or
+  split it up.
+* If none of the above worked and the PR has been stuck for more than 2 weeks,
+  the owner should bring it to the OpenFeatures [meeting](README.md#contributing).
+
+## Automated Changelog
+
+Each time a release is published the changelogs will be generated automatically using `release-please`.
+
+## Design Choices
+
+As with other OpenFeature SDKs, ruby-sdk follows the
+[openfeature-specification](https://github.com/open-feature/spec).