v0.8.0-rc1

Added

• Command for backfilling room history from Telegram.
• ARM64 support in docker images.
• Optional end-to-bridge encryption support (#403). See page on wiki for more info.
• Bridging for Telegram dice roll messages.

Fixed

• Riot iOS not showing stickers properly.
• Updated to Telethon 1.13 to fix bugs like #443.