Add docs to the user manual about the terminal key bindings

Summary:
Also mention the manual on the Keyboard tab in the Edit Profile Dialog
to make it more discoverable for users.

Sources used while writing this documentation:
  - data/keyboard-layouts/README.KeyTab
  - doc/user/README.keyboard
  - https://invisible-island.net/xterm/ctlseqs/ctlseqs.html
  - https://www.vt100.net/docs/vt100-ug

Reviewers: #konsole, hindenburg, yurchor, ltoscano

Reviewed By: #konsole, hindenburg

Subscribers: kde-doc-english, hindenburg, #konsole

Tags: #konsole

Differential Revision: https://phabricator.kde.org/D12015