Allow adding custom Riot URL(s)
User should be able to set a custom Riot (web app) URL as an alternative to riot.im.
Needs #2 "remember my preference", for usability.
This would help fairly casual users to use their preferred Riot-web instance. (What we refer to as a "preference" might be a hard requirement for them in pracice.)
This still presents a barrier to first time and novice users, but lowers the barrier.
Advanced extras: allow multiple alternative URLs; allow associating each URL with a given server-name part of server-scoped room alias and user links.