Add Link Header for WHIP/WHEP

[a-wing]

For WHIP: https://www.ietf.org/archive/id/draft-ietf-wish-whip-01.html#section-4.4

For WHEP: https://www.ietf.org/id/draft-murillo-whep-02.html#section-4.4

For example:

mediamtx

https://github.com/bluenviron/mediamtx/blob/30b7245bb97e2796a279179b05b2cb8913627d64/internal/whip/link_header.go#L23-L37

whip-whep-js

https://github.com/medooze/whip-whep-js/blob/d0cba4f598c54e4a03a13bedb7f60fae8aaea51d/whip.js#L87-L139

[a-wing]

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Link#encoding_urls

[a-wing]

8fcdc40c2d88b06b3a9542b4de9dfd4147a40b8f and 9a38f2b08157298885a807cb0d73635dc4ec22f2