Link to markup cheat sheet (BB-5005)

Aryeh Leib Taurog avatarAryeh Leib Taurog created an issue

In addition to the preview box (#4384), it would really help to have at least a link to a markup cheat sheet, so I don't have to go looking for it on my own, as well as a description of the markup for linking to a changeset, a user, or an issue.

See stackoverflow for a great example of a helpful, unobtrusive set of markup cheatsheets integrated right into the editor.

Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.