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