v0.12.3-rc.1

Full Changelog

• Fix overflowing login/register buttons on some languages issue #4804
  #4858
• Update vector-im to riot-im on Login
  #4943
• lets let people know that the bug report actually sent properly :)
  #4910
• another s/vector/riot/ in README
  #4934
• fix two room list regressions
  #4907