Release notes for Grafana 8.4.0-beta1

Alerting: Support WeCom as a contact point type. #40975, @smallpath
Alerting: UI for mute timings. #41578, @nathanrodman
Alerting: add settings for peer reconnection in HA mode. #42300, @JohnnyQQQQ
Auth: implement auto_sign_up for auth.jwt. #37040, @Roguelazer
Dashboard: Add Show unknown variables toggle to dashboard settings. #41854, @hugohaggmark
Instrumentation: Logger migration from log15 to gokit/log. #41636, @ying-jeanne
MSSQL: Change regex to validate Provider connection string. #40248, @ianselmi
MSSQL: Configuration of certificate verification for TLS connection. #31865, @mortenaa
Middleware: Don’t require HTTPS for HSTS headers to be emitted. #35147, @alexmv
Navigation: Implement Keyboard Navigation. #41618, @axelavargas
News: Reload feed when changing the time range or refreshing. #42217, @ashharrison90
UI/Plot: Implement keyboard controls for plot cursor. #42244, @kaydelaney