Updated content script to use the `beforeinput` event

[tdulcet]

• Updated the content script to use the beforeinput event instead of the keydown and keyup events for autocorrection (see https://github.com/rugk/unicodify/issues/4#issuecomment-831841205).
  • Originally designed as a fix for #4. While it does not fix that, it may fix other site issues.
  • Improves the performance.
    • Does the autocorrections before the browser modifies the DOM tree (see here).
  • Greatly improves Android capability.
    • Eliminates dependence on the keyboard events which are poorly supported on Android (see Firefox Bug 1104817 and Chrome Bug 118639).
  • Requires Firefox/Thunderbird 87.

@rugk – I think this could be merged sometime after 2021-11-2 when Firefox/Thunderbird 78 will no longer be supported (see https://github.com/rugk/unicodify/issues/4#issuecomment-806543762). I would also need to make a companion PR for the Awesome Emoji Picker.

[tdulcet]

Some minor code-style comments, because that code is really hard to understand. It's likely because it is just a complex piece of code, but we can do better to use understandable variable names etc. 🙂

Thanks. I made your requested changes in https://github.com/rugk/unicodify/pull/37/commits/9d9b4035b13c4ccdc3263e8931e3e1f3e1c592cb. I know am bad at naming stuff, so please feel free anytime to suggest better names for things. 😉