Merge providers from Bazarr

[getzze]

They seem to maintain a long list of providers:
https://github.com/morpheus65535/bazarr/tree/master/custom_libs/subliminal_patch/providers

[ptrcnull]

that's not gonna be possible, unless all their contributors relicense their contributions under MIT ( which Subliminal uses )

[getzze]

ah yes... Then we will have to revive old PRs here :)

[getzze]

I was thinking what was the best way to include other providers and I think it makes sense to create a subliminal-providers package with the other providers, only keeping key providers in this package.
Like that subliminal-providers could have another release schedule and a faster review process, keeping subliminal "clean".

What do you think?