Expose onBlur event

[jtbandes]

I would like to clear the selection when the terminal loses focus. I was able to make it work like this:

    (terminal as any)._core?.onBlur?.(() => {
      terminal.clearSelection();
    });

It would be nice to expose this onBlur event on the public Terminal interface so people don't have to use private API for it.

(Probably onFocus too, I just didn't happen to need that one.)

[Tyriar]

I think in the past we didn't add this as you can just add regular dom listeners to Terminal.element after calling Terminal.open:

xterm.js/typings/xterm.d.ts

Lines 831 to 834 in 41e8ae3

	/**
	* The textarea that accepts input for the terminal.
	*/
	readonly textarea: HTMLTextAreaElement | undefined;

[jtbandes]

I tried that as well, but it didn't work. Example: https://codesandbox.io/p/sandbox/xtermjs-test-forked-rfznf7

[jtbandes]

Ah I see, it works with terminal.textarea but not terminal.element. Thanks! 🎉