[ie/beacon] Add extractor for Beacon.tv

[Deukhoofd]

IMPORTANT: PRs without the template will be CLOSED

Description of your pull request and other information

Add an extractor to support downloading from https://beacon.tv, a new media website launched by Critical Role yesterday.

This website places a JSON in an HTML tag with a specific ID and type. This tag is extracted, the JSON is parsed, and the m3u8 URL and metadata are retrieved from the JSON.

Authentication on the site is done through cookies. This means that downloading videos that require authentication currently depends on the --cookies-from-browser command line flag. Videos that are public can be downloaded without this flag.

Template

Before submitting a pull request make sure you have:

• [x ] At least skimmed through contributing guidelines including yt-dlp coding conventions
• [x ] Searched the bugtracker for similar pull requests
• [x ] Checked the code with flake8 and ran relevant tests

In order to be accepted and merged into yt-dlp each piece of code must be in public domain or released under Unlicense. Check all of the following options that apply:

• [x ] I am the original author of this code and I am willing to release it under Unlicense
• I am not the original author of this code but it is in public domain or released under Unlicense (provide reliable evidence)

What is the purpose of your pull request?

• Fix or improvement to an extractor (Make sure to add/update tests)
• [x ] New extractor (Piracy websites will not be accepted)
• Core bug fix/improvement
• New feature (It is strongly recommended to open an issue first)

[Deukhoofd]

Abandoning, as I just realized there's a way cleaner method to do what it needs to do.

[bashonly]

You can push to the same branch and repurpose/reopen this PR

[Deukhoofd]

Nevermind the earlier message. I tried to use the Beacon API at https://beacon.tv/api/graphql. This works generally, and would simplify the flow of the code a lot. Unfortunately, for authenticated requests this requires an authentication token. This token is not retrievable from cookies, and requires a fairly complicated Oauth flow (using Memberful, a Wordpress plugin). This flow involves captions and other annoyances I wasn't able to work around.

While the direct API handling would have been a lot nicer, scraping the information from the HTML also functions. As such this should be fine for now.