Improve Documentation

[micimize]

IMO #648 improves on documentation rigor significantly, but there are still probably weak points like:

• [ ] It would be nice to have a static site #59
• [ ] We still fall back on saying "it's like apollo" sometimes #544
• [ ] The readmes are kind of weak as "getting started" guides tbh
• [ ] Embedded runnable examples
• [x] Update policies section
• [ ] Add explanation of reasoning behind immutability #633
• [ ] Add more info on context + example of how to set headers in context per-request #633
• [x] Add docs on rebroadcast behavior and why subscription rebroadcasting doesn't make sense

Examples:

• [ ] Add android INTERNET permissions to examples so they work in release mode

I want to consolidate these other issues here to minimize broad/ill defined "better docs plz" issues

[micimize]

#608 has some docs discussion / links as well

[micimize]

consolidating #657

Embedded runnable examples would be dope. We'll need [embedded api docs with library support] (https://github.com/rrousselGit/flutter_hooks/issues/118) though, which I'm willing to wait for official support for

[micimize]

consolidating #748 as it is smol

[micimize]

The problem with rebroadcasting subscription results when the cache changes is that subscriptions are already a stream, so semantically each should be treated as a separate event. A rebroadcast would look like a new event, and thus break the the contract.

Theoretically, if RebroadcastPolicy is made its own concept, then allowing the user to explicitly set subscriptions to rebroadcast would be a fine feature to implement. Probably will be some time before that is implemented though.

This problem is similar to the problem of #774 – mutations should not do a cache round-trip either by default.