Allow to stop test speaker

[romainlq]

Pre-Flight Checklist

Please use this checklist to avoid spamming:

1. [x] I am not asking a question => use the Discord if you are
2. [x] I have checked that someone else has not suggested this using the search bar
3. [x] My feature request is not one of the commonly suggested features:

• Adjustable voice radius
• Mobile support
• Linux / MacOS support
• Itch.io support

Is your feature request related to a problem? Please describe.

When I test my speaker I can not stop the test and have to hear the whole sound

Describe the solution you'd like

I should be able to stop the test speaker and not have to hear the whole sound

Describe alternatives you've considered

Additional context

I made a Pull request in order to fix it --> #592