Enable Towncrier

[manuroe]

part of #4393.

Output with current changes:

Changes in 1.2.3 (2021-08-09)

✨ Features

• Voice messages: Remove labs setting and enable them by default. (#4671)

🙌 Improvements

• Settings: The notifications toggle no longer detects the system's "Deliver Quietly" configuration as disabled. (#2368)
• Room: Remove the green border from direct message room avatars. (#4520)
• Settings: Adds a link to open the Settings app to quickly configure app notifications. (#4575)
• VoIP: Additional changes on call tiles. (#4642)
• Voice messages: Allow voice message playback control from the iOS lock screen and control center. (#4655)
• Voice messages: Stop recording and go into locked mode when the application becomes inactive. (#4656)
• Voice messages: Improve audio recording quality. (#4671)

🧱 Build

• CHANGES.md: Use towncrier to manage the change log. More info in CONTRIBUTING. (#4393)
• Add a script to initialize quickly and easily the project. (#4596)

📄 Documentation

• Convert CHANGES to MarkDown. (#4393)
• Add reference to AppIdentifiers.xcconfig in INSTALL.md. (#4674)

[pixlwave]

LGTM 👍

I'm presuming CHANGES.md isn't meant to use links for all the issue #s as they're all in this repo.