[Pas2js] New small demo

[Michael Van Canneyt]

Hi,

Some of you may have seen in git that I added a small demo to demonstrate
audio playing. I also put it online at:

https://www.freepascal.org/~michael/pas2js-demos/player/

Demonstrates quite nicely how easy it is to quickly piece something together
with pas2js and the Web APIs.

Enjoy !

Michael.

PS. The music does not reflect my personal taste, I needed to find some
royalty-free music ;-)