Change music to be time-dynamic

[ShamblesSM]

When the player reaches around 0:14, the "danger" music should start. Likewise, when the time added results in the total time being over 14 seconds, it should go back to normal.

There should be some sort of BPM counter (for OpenSMCE flexiblity reasons), or wait for the loop to end.

• Add the music assets
• Set baseline for time-dynamic music
• Play the least intense versions a couple of time first before moving on to the more intense version, and have it reset in case of the 15-second mark

[ShamblesSM]

Partially implemented in 21b98aa