Add emoji reaction support

This is already supported in Pleroma-FE.

I'd like to take a stab at implementing this.

@lanodan I know mastofe is a "distribution" of glitchfe, so is there any "proper" way of going about adding a feature like this?

Like documented in the readme you target the rebase/glitch-soc branch. And while patching it try to keep the modifications to a minimum to reduce future conflicts.