Fixed typos in AR CHANGELOG
Merge pull request #10228 from prathamesh-sonpatki/AR-Typos

Fixed typos in AR CHANGELOG
Fix documentation to the custom Deprecator

[ci skip]
The third argument of deprecation_warning is always optional

[ci skip]
replace match with get verb in ActionController::Metal
Merge pull request #10230 from gaurish/remove-match

replace match with get verb in ActionController::Metal
converts the project README to Markdown

We tend to use Markdown for everything but the API, the
README is no longer used as the home page of the API
after 7a5aa72, so we can now migrate it.
editorial touch, remove these dots