Allow additional shortcuts for submitting gum write

[annervisser]

Is your feature request related to a problem? Please describe.
While Ctrl+d is a unixy way of exiting a program, it doesn't feel logical to me as a "submit".

Describe the solution you'd like
I'd love some additional shortcuts for saving my text, Ctrl+s and Ctrl+x (Nano) come to mind.

It would also be helpful if the shortcut(s) were listed in the description of gum write --help

Describe alternatives you've considered
n/a

Additional context
Current documentation:

Note: CTRL+D is used to complete text entry. CTRL+C and esc will cancel.

Current output of gum write --help:

Usage: gum write

Prompt for long-form text

Flags:
 [...]

Style Flags
 [...]

[octoshrimpy]

second this. shift-enter is another one I recommend. relevant to #286 and #433

[caarlos0]

I believe shift+enter requires kitty keyboard, which is coming on v2 (cc/ @aymanbagabas)

that said, I also don't like ctrl+d being used for this, but I agree ctrl+s and ctrl+x are better options

[meowgorithm]

yep shift+enter will be possible in with Bubble Tea v2, however also keep in mind that in many terminals and multiplexers the feature simply won't be available (at least not by default). We can offer that when it is available.

Anyway, it will probably be helpful to show the options on the onscreen help (--show-help).

One question: isn't "submit" currently just enter?

[caarlos0]

One question: isn't "submit" currently just enter?

you're right!

but there's another 'weirdness': ctrl+j is used to enter a new line, which I also don't like (and conflicts with my tmux mappings)... would probably bind that to shift+enter as well on v2, which seems to be more easy to figure out