Hi there,
Thanks for your feedback.
I added an option to set the volume level. The options page could be nicer but I'll rework that later, hopefully.

Hi,
Hmm I'm not sure what makes Avast think that.
The only permission it requires from the browser is the ability to display notifications.
If you can, don't take my word for it, the source code is available, not minified, not offuscated in anyway and doesn't use third party code.
Don't hesitate to post an issue on github if it persists.