Fix newfound bugs with rich mentions + user suggestions

• fixed alignment issues with firefox
• fixed poast mentions not having a space
• fixed spacings in mention-line overall, should be more more consistent now
• added options to disable (opt-out) bold text of own mention and to enable (opt-in) of (You)s, instance-default for both.
• fix inline image sizes
• fix & in links
• user popovers in interaction lists do not emojify names
• write some more tests