doc: Revise instance rules for compliance and stability

[unixfox]

Updated rules for instances to include new requirements on playback stability and IP rotation due to YouTube blocking more aggressively public instances.

Related: #685 (comment)

[mv12star]

@unixfox In my humble opinion, rules 5 and 16 conflict. As discussed in #685 , my wannabe-public-instance does have good playback stability, at the expense of slightly lower streaming quality.

From a UX perspective, facing constant blocks, downtime, and companion errors is not ideal, while making direct requests to googlevideo at the expense of getting 360p is. Hence, I believe the subsequent reduction in quality of streaming shouldn't be considered as a "restriction" imposed by the maintainer in this case, but rather a limitation from Invidious companion itself.

Furthermore, I believe that adding an instance that does not proxy YouTube videos could be an interesting option, or at least give a grace period of a few days being added to the instances API, and checking its performance before fully discarding it.

TLDR: Please make rule 16 more lenient :)

[unixfox]

Proxying or not doesn't change the internal metrics that dictate if Youtube consider your IP address "malicious".

Proxying or not still requires to reach the same specific playback endpoint.

Nerdvpn used to be 360p only like 8 months ago, he still had to rotate the IP frequently. Same as right now.

Unless things changes in the future, something I'm working on, the current rules reflect the harsh reality of running a public instance. There are no other ways, all the other ways have already been explored.