feat(supertab): modkey timeout for rotate key press

[lewurm]

Snippet from documentation diff:

In addition to the keycodes above a modifier (modifier-key) can be configured that is pressed simultaneously with the configured keycodes, and then held until another keycode is send via an encoder action or a timeout (mod-timeout-ms) is reached.

Example for application switching:

sm: supermods {
    compatible = "zmk,behavior-sensor-rotate-key-press";
    label = "encoder supermod";
    #sensor-binding-cells = <2>;
    modifier-key = <LWIN>;
    mod-timeout-ms = <1200>;
};
[...]
sensor-bindings = <&sm TAB LS(TAB)>;

Example for selecting characters in an text editor:

hlm: highlightmods {
    compatible = "zmk,behavior-sensor-rotate-key-press";
    label = "encoder highlighter";
    #sensor-binding-cells = <2>;
    modifier-key = <LSHFT>;
    mod-timeout-ms = <500>;
};
[...]
sensor-bindings = <&hlm RIGHT LEFT>;

[caksoylar]

This seems pretty useful! Related: #997

Regarding documentation, I am curious if we should have a policy about including gifs. In my opinion it might be too distracting (and also cause large size page loads). @zmkfirmware/docs what do you think?

[lewurm]

This seems pretty useful! Related: #997

Thanks, I haven't seen this yet. Reading that, it makes more sense to split the idea of this PR into two separate things:

1. As suggested in Feature request: Automatically held/released mods for certain keycodes for Alt-Tab window switching #997, implement another behavior that has this "mod holder" functionality.
2. Add a new behavior forsensor-bindings such that not only the &kp behavior can be used, but any arbitrary one. Apart from the suggested "mod holder" behavior I would like to be able to map &rgb_ub to the rotatry encoders (mentioned in RGB Underglow improvements #65 ).

Of course, I don't know how to actually implement those nicely 😉 I'll keep this PR open for visibility, so if someone wants the funcitionality today it can be cherry-picked, but it should probably not be merged as-is.