Update main-fr.json
Update main-fr.json

Add missing translation.
Improve French language / French styling.
Fix typos.
jitsi/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet,gpolitis/jitsi-meet,gpolitis/jitsi-meet,gpolitis/jitsi-meet,gpolitis/jitsi-meet,gpolitis/jitsi-meet,jitsi/jitsi-meet