Add extra shortcuts for builtins

[9999years]

• input_go_word_left: alt-b
• input_go_word_right: alt-f
• line_down: ctrl-j
• line_up: ctrl-k
• panel_left_no_open: ctrl-h
• panel_right_no_open: ctrl-l

These don't conflict with any existing builtin shortcuts and users can override them if they want.

[Canop]

Those look a little too personal, apart maybe the line_down and line_up. Where do the alt-f for input_go_word_right come from ?
Unless there's some support from other users I'm reluctant to add those: if they're just personal, they can be just in your config.

Other users are invited to give their opinion.

[9999years]

alt-b and alt-f for word-back and word-forward come from Emacs, although they're supported in many terminals as well.

[ghost]

alt-b and alt-f for word-back and word-forward come from Emacs, although they're supported in many terminals as well.

Is it possible to have readline(3)-like binding when in command mode? Helix editor did it.

[Canop]

The right solution to me seems to be the addition of a commented-out block of settings in the default configuration, similar to what we already have for vim-like shortcuts: https://github.com/Canop/broot/blob/main/resources/default-conf/verbs.hjson#L113