Add support for keypress events

To be able to have the component rerendered on keypresses and get the keys.

Ink would need to do readline.emitKeypressEvents(stdin); in https://github.com/vadimdemedes/ink/blob/master/src/components/App.js#L61 And it requires raw-mode.

After enabling the above, Ink could do something like this internally:

process.stdin.on('keypress', (str, key) => {
    if (key.ctrl && key.name === 'f') {
        console.log('foo')
    }
})

My initial idea was to expose a useKeypress() React hook. @vadimdemedes suggested we could just expose the keypresses by default if raw-mode is activated, as the output is being diffed anyway, so the cost is negligible.

[sindresorhus]

I would like useKeyHandler to be built-in. It’s a very common need.

[vadimdemedes]

Released 2.4.0, which adds useInput hook.