Add shortcuts for calling
Add shortcuts for calling

a - toggle audio on/off
v - toggle video on/off
p - switch to participants tab
c - switch to chat tab

Signed-off-by: Joas Schilling <ab43a7c9cb5b2380afc4ddf8b3e2583169b39a02@schilljs.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed