About: Fix typo's in the about section.

Created by: absoludity

I'd started a branch with typo's that I noticed, then thought it may make sense to actually use cspell.

With this PR I've added cspell and used it to fix all typos in the about section (adding vocab to the cspell config for now), but don't want to spend more time on it now (I'd rather learn), so will leave the rest (when I've time I'll get aider or similar to do the manual labour :P)

I've ignored the about/Meetings.md as I don't want to change meeting notes.