Update config-cheat-sheet.en-us.md (#8497)

* Update config-cheat-sheet.en-us.md

Add more information on configuring URI hyperlink rendering for Markdown.

* Update config-cheat-sheet.en-us.md

Update description as suggested by @guillep2k

* Update docs/content/doc/advanced/config-cheat-sheet.en-us.md

Co-Authored-By: guillep2k <[email protected]>

Author: 2 people

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -108,6 +108,9 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 ## Markdown (`markdown`)
 
 - `ENABLE_HARD_LINE_BREAK`: **false**: Enable Markdown's hard line break extension.
+- `CUSTOM_URL_SCHEMES`: Use a comma separated list (ftp,git,svn) to indicate additional
+  URL hyperlinks to be rendered in Markdown. URLs beginning in http and https are
+  always displayed
 
 ## Server (`server`)