Add an option to remove spell checker

The spell checker is getting annoying. Sometimes I speak a foreign language or misspell words on purpose. The spell checker tick box which appears when I right click is "already turned off", but the red underlines still appear when I'm typing my status, about me, user notes, role names, emoji names, server names, text in code blocks, basically anything other than a plain text message.

Add an option to globally remove the spell checker.