Consider using python-piper instead of the platform-specific binaries

[Martin-Laclaustra]

Piper can be instaled/used with:

pip install piper-tts

This could make installation easier adding a requirements.txt file, which would be platform-independent and similar to other extensions.
The line that defines the executable should change accordingly:

piper_tts/script.py

Line 15 in c22c6b1

piper_path = root_dir / 'piper/piper'

Some tests would be needed to assess whether performance is impacted and whether it works in all platforms.

I will not be advancing this issue soon, thus contributions are welcome.