Thock v1.21.0

What's Changed

• thock: Keep the desk-only chat rules out of the phone's prompt by @DiegoTavares in #148
• thock: Bound how long the phone holds the change feed by @DiegoTavares in #149
• thock: Version the phone app 1.0 (build 15) by @DiegoTavares in #150
• thock: Add reminders, rung on the desk and the phone by @DiegoTavares in #151
• Release 1.21.0 by @DiegoTavares in #154

Full Changelog: v1.20.0...v1.21.0