Add dependencies for building docs

[DarkLight1337]

I found that I couldn't build the documentation just from installing dev and test dependencies. It turns out that pyproject.toml currently does not specify the dependencies for building the documentation.

This PR adds the doc extra which includes such dependencies, making it easier to set up the environment for building documentation.

[martindurant]

This essentially replicates the environment in https://github.com/fsspec/filesystem_spec/blob/master/docs/environment.yml . It seems like a bad idea to have the environment in two places.

[DarkLight1337]

This essentially replicates the environment in https://github.com/fsspec/filesystem_spec/blob/master/docs/environment.yml . It seems like a bad idea to have the environment in two places.

I have addressed this in the latest commit.

[martindurant]

  - (b'{"key": "value"}')
  ?           -
  + (b'{"key":"value"}')

Apparently the JSON serialization changed format slightly

[DarkLight1337]

  - (b'{"key": "value"}')
  ?           -
  + (b'{"key":"value"}')

Apparently the JSON serialization changed format slightly

Seems that this was introduced by #1562. Imo we should fix that in a separate PR.

[martindurant]

The tests passed at the time, so some version got updated. Since it's a one-character fix, I'd be happy to see it here.

[DarkLight1337]

The tests passed at the time, so some version got updated. Since it's a one-character fix, I'd be happy to see it here.

The problem is not that trivial. Seems that the separator in json.dumps depends on whether json or ujson is being used to serialize the data. We may need to pass the json module to use to ReferenceFileSystem, in order to ensure that the tests are consistent regardless of which module is available.

[martindurant]

It's find to importorskip("ujson") for the test, and we know that the package will be there in CI.

[DarkLight1337]

It's find to importorskip("ujson") for the test, and we know that the package will be there in CI.

I found a better solution, which is to use the same json module to encode the dictionary for the reference value inside the test.