Store app command ids on CommandTree

[Soheab]

Summary

As it was desired, I have written an implementation that stores app command ids on the CommandTree and keeps them updated via sync, fetch and on callback. Also added two new methods to get the ID and return the mention format.

Currently as a draft because I am not sure if the current impl is the best way to this and would like some feedback on it, ignoring the left over comments/methods but it does work.

Checklist

• [x] If code changes were made then they have been tested.
  • [x] I have updated the documentation to reflect the changes.
• [ ] This PR fixes an issue.
• [x] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)