Move documentation to github

With all of the improvements to AppSync, it is sometimes difficult to glean which features are new/improved from the current documentation. Individual pages don't currently have last modified timestamps. I do find AWS Amplify's documentation to also be a bit unwieldy, but I appreciate that they keep everything within Github so changes are easy to spot. Would it be possible to move documentation to Github as well or at minimum include timestamps / change history? I am sure that there are other solutions that would help mitigate these issues as well if neither are viable.

Thank you for you for consideration.

No file or test is identified; begin by reviewing how the current AppSync documentation is maintained and compare it with the AWS Amplify GitHub documentation approach mentioned in the issue. Done should be a decided, scoped documentation change that either moves the documentation to GitHub or adds timestamps and change history.

Written by the indexing model from the issue text.