Black applied.

Tests fixed.

Temporary disable Pylint-quotes due to the bug it has.

Got rid of the deprecated Pydocstyle.

Make Poetry use active Python for compatibility with Pyenv.

README.md: Fixes in the "Development" section.

Buildfix + upgrade of dependencies.

Merge branch 'switch-from-graphql-transport-ws-to-graphql-ws-subprotocol'

Post-review fixes, primarily comments and formatting.

Moved websocket close code processing from transport for tests to the client for tests. Cosmetics.

Cosmetics after review.

Added error handling according to protocol description.

Cosmetics and comments.

Fix the dependence of the client interface on the protocol.

Possibility to select subprotocol for GraphqlWsTransportAiohttp added.