[FEATURE]: Document Shift+Enter key binding for Alacritty and Tmux

[angelcervera]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

The current documentation only have information about how to enable Shift+Enter on Windows terminal. I would like to have information about how to do it in other setups, lile Alacritty and Tmux.

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• shift+enter on tmux not working #167: shift+enter on tmux not working (same topic - tmux)
• shift-modified keybindings ignored inside tmux #336: shift-modified keybindings ignored inside tmux (same topic)
• Shift-return does not input newline since 1.0 #4046: Shift-return does not input newline since 1.0
• shift+enter keybinding not working #1505: shift+enter keybinding not working

For keybind-related issues, please also check our pinned keybinds documentation: #4997