Make a new `beat_speed_modulated` example

[rand00]

trafficstars

Copy the beat example to a new beat_speed_modulated example-directory, and add another beat in it by calling Fry.Beat.Make (call the returned module Beat_speed_mod).

Then use Beat_speed_mod.s with S.map (and e.g. the sin function) to modulate the speed of Beat by passing the signal as bpm_s.

[AryanGodara]

Can I work on this as well @rand00 , after making progress on #1 , since these two are different type of tasks, I want to work on both 😅

[rand00]

It would be best if you finish one at a time (: In the meantime others can still ask to work on this issue

[kamtoeddy]

@rand00, Please can I work on this issue?

[rand00]

@kamtoeddy Hey! Yes, as @AryanGodara isn't done with the other PR yet, just start on this (: