add pass_meta_key decorator

[davidism]

Extensions using Context.meta can use pass_meta_key to create decorators for passing their data to callbacks. The doc_description parameter can be used to add a specific description of the object, so that the decorator's docs can be included in the extension's docs.

# in the extension
from click.decorators import pass_meta_key
pass_auth = pass_meta_key("click-auth.auth", doc_description="the :class:`ClickAuth` object")

# in the extension's docs
pass_auth.__doc__
Decorator that passes the :class:`ClickAuth` object as the first argument to the decorated function.

# in the user code
@pass_auth
def list_prs(auth):
    ...

Also changed docs config so typing information is shown next to parameter descriptions instead of in the signature. https://pallets-click--1807.org.readthedocs.build/en/1807/api/#click.decorators.pass_meta_key

• fixes @pass_meta_key decorator #1739

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• Add .. versionchanged:: entries in any relevant code docs.
• Run pre-commit hooks and fix any issues.
• Run pytest and tox, no tests failed.

[eshaan7]

Really glad that you liked my idea. :D