chore: make docs MDX-compatible (#1724)

Required since Gatsby ingests the .md files as MDX, and GFM syntax causes the build to break.

Author: samueldemoura

docs/contributor-info/pull-requests.md

@@ -37,7 +37,7 @@ When making doc changes, we want the change to work on both the gitbook and the
 
 ### Links to other docs:
 
-- When making references to doc files, use a full URL to <https://www.shakacode.com/react-on-rails/docs>, for example:
+- When making references to doc files, use a full URL to [https://www.shakacode.com/react-on-rails/docs](https://www.shakacode.com/react-on-rails/docs), for example:
   `[Installation Overview](https://www.shakacode.com/react-on-rails/docs/additional-details/manual-installation-overview/)`
 
 - When making references to source code files, use a full GitHub URL, for example:

docs/guides/tutorial.md

@@ -19,8 +19,8 @@ You can find it here:
 
 By the time you read this, the latest may have changed. Be sure to check the versions here:
 
-- <https://rubygems.org/gems/react_on_rails>
-- <https://www.npmjs.com/package/react-on-rails>
+- [https://rubygems.org/gems/react_on_rails](https://rubygems.org/gems/react_on_rails)
+- [https://www.npmjs.com/package/react-on-rails](https://www.npmjs.com/package/react-on-rails)
 
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