Adds 'Problem saving your document' section to FAQ (#1931)

* Adds 'Problem saving your document' section to FAQ

* Corrects links to be relative where possible.

* Corrects error message formatting.

* Corrects error message formatting in a more correct manner.

content/docs/errors/faq.md

@@ -2,6 +2,24 @@
 title: 'FAQ: Content API Errors'
 ---
 
+## There was a problem saving your document
+
+When using Tina Cloud without [Editorial Workflow](/editorial-workflow), you need to ensure that the [Tina Cloud App](https://github.com/apps/tina-cloud-app) is able to commit to the selected branch of the repository.
+
+If it cannot, you will see an error of the following form:
+
+```text
+Tina caught an error while updating the page:
+
+Error: Unable to fetch, errors:
+    Error in PUT for src/pages/some-page.md
+```
+
+To fix this issue, either:
+
+- [Modify the branch's protection rule](https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/managing-protected-branches/managing-a-branch-protection-rule#editing-a-branch-protection-rule) to allow the Tina Cloud App to bypass the [require a pull request before merging](https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/managing-protected-branches/about-protected-branches#require-pull-request-reviews-before-merging) rule, or
+- Enable [Editorial Workflow](/editorial-workflow) to create PRs on the branch.
+
 ## Invalid or undefined branch
 
 The current branch that Tina is using is invalid or undefined. Double check that the correct branch is selected and it does in fact exist.