When user enters meeting with music already playing, an event listener is set
to play the music only after user interaction.
Also, to keep timer more cohesive and reduce complexity of the condition for
playing music, timer automatically stops after 90% of users notify that the
timer has expired.
Adds a music player for ambient sound which can be turned on and off using a
toggle located inside timer panel. When stopwatch is selected, this toggle is
automattically turned off.
