Backporting widevine-installer

Hey there,

I am about to upload widevine-installer to backports-NEW. 
widevine-installer is an installer for the widevine CDM library on arm64 
platforms. It recently migrated to testing, and it was never in stable. 
By uploading it to trixie-backports, stable arm64 users will be able to 
install widevine on their systems, which in turn will allow them to 
reproduce protected content on services such as Spotify, Netflix, Amazon 
Prime, etc.

Cheers!