refactor: separate some hotkey code into a library

[WofWca]

Like this, for example:

jumpcutter/src/hotkeys/eventTargetIsInput.ts

Lines 21 to 39 in 81b4e50

	/**
	* If a key is pressed while typing in an input field, we don't consider this a hotkey.
	* Filter criteria is yoinked from
	* https://github.com/ccampbell/mousetrap/blob/2f9a476ba6158ba69763e4fcf914966cc72ef433/mousetrap.js#L1000
	* and alike libraries. Another reason to rewrite all this using a library.
	*
	* TODO how about we also/instead check if the target element is a parent of the video element that we're controlling?
	*/
	export function eventTargetIsInput(event: KeyboardEvent): boolean {
	const t = event.target as Document | HTMLElement;
	return (
	['INPUT', 'SELECT', 'TEXTAREA']
	// @ts-expect-error 2339 for performance because doing `'tagName' in t` would be redundant, because
	// it is present most of the time.
	.includes(t.tagName)
	// @ts-expect-error 2339 same as above
	|| t.isContentEditable
	);
	}

As stated in the comment, the criteria is already taken from another library.