Document the enduser feature pylsp-mypy provide to python-lsp-server

[LuisBL]

python-lsp-server throught jedi provide out of the box type-hinting
Cf. https://jedi.readthedocs.io/en/latest/docs/usage.html#type-hinting

The documentation could be improved for end-users of pylsp-mypy to explain pylsp-mypy will provide to python-lsp-server ...

[LuisBL]

Could be something like this