Ability to customize keyboard shortcuts

[Amnish04]

In #826, I added a CTRL+l keyboard shortcut to clear chats when focused on the prompt textarea. However, @tarasglek ran into an issue where he started losing his chats as this shortcut overlaps with "focus url bar" shortcut in windows.

I addressed that with a temporary fix in #866 by disabling the shortcut for windows users, but I think a proper fix would be to allow users to customize keyboard shortcuts.

We could add a new section in the settings modal and allow users to:

1. Enable/disable specific shortcuts.
2. Configure custom key bindings for shortcuts.

[Amnish04]

@tarasglek @humphd Should we close this as we decided to fully revert CTRL+l shortcut?