docs: add pipeline stattus & coverage report badges

README.md

 # Import and Playlist Daemon
 
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 Tank implements an AURA import and playlist daemon. Uploads can be normalized
 based on the [loudnorm](https://k.ylo.ph/2016/04/04/loudnorm.html) Loudness
 Normalization. Resulting files are served to Aura Engine via some configured