[FEAT] Add ability to play sounds through annotation text

[develroo]

Not sure how feasible this is but it does seem like it could be kinda cool.

Atm you can display image though the annotation text by using markdown. eg.

![Some image](https://myserver.org/assets/images/myimage.jpg)

In theory, you can do a similar thing with sound as outlined on this page. You could then place audio assets on a web server and serve them to PA as needed.

Not sure how easy it would be to add this functionality, but just thought I would put it out there in case anyone else is interested.

Feedback welcome.