Implement /tv/{channel}/feed endpoint

[trevorbayless]

Implements the /tv/{channel}/feed endpoint and adds TypeDicts.

NOTE:
I attempted to add a test for this (test_tv.py) but for some reason vcrpy hangs during make test_record when hitting the test (possibly because this is a stream endpoint?). In the linked test, I clipped the stream at the first two results as this endpoint is an infinite stream.

Interestingly enough, if you remove @pytest.mark.vcr the test passes, but we want this as a cassette. I was able to manually create a cassette for this (TestTV.test_stream_bullet_tv.yaml) which works, but would be problematic if the cassette needs to be regenerated so I assume this isn't something we want to manually add. vcrpy is new to me, so if anyone has an idea on what the issue might be please let me know and I'll gladly add a test for this.

Checklist when adding a new endpoint

• Added new endpoint to the README.md
• Ensure that my endpoint name does not repeat the name of the client. Wrong: client.users.get_user(), Correct: client.users.get()
• Typed the returned JSON using TypedDicts in berserk/types/, example
• Tested GET endpoints not requiring authentification. Documentation, example
• Added the endpoint and your name to CHANGELOG.md in the To be released section (to be created if necessary)

[kraktus]

Hey, sorry for the delay, I checked and found no documentation on how to handle infinite stream. Since it's not a big deal I'll merge, thanks!