misc: unify terminology

smart quotes {“,”,’}
remove spaces in keyboard shortcuts, eg Ctrl + F → Ctrl+F
add participant → invite member
A(n) [type] error occurred while [attempting to] {verb} {noun}.
avatar → profile picture
ban → block
join in… → join with…
mute camera → stop camera
plugin → extension
request → invitation
unmute camera → start camera

GitLab: #1730
Change-Id: Ied169aea3b15b341ff467bc838c70da6a3d5050f