Render PEP-257-style docstrings to markdown

[Gankra]

https://peps.python.org/pep-0257/

This format isn't explicitly specified in the PEP but it is alluded to and used in the stdlib. For instance:

def filterwarnings(action, message="", category=Warning, module="", lineno=0,
                   append=False):
    """Insert an entry into the list of warnings filters (at the front).

    'action' -- one of "error", "ignore", "always", "default", "module",
                or "once"
    'message' -- a regex that the warning message must match
    'category' -- a class that the warning must be a subclass of
    'module' -- a regex that the module name must match
    'lineno' -- an integer line number, 0 matches all warnings
    'append' -- if true, append to the list of filters
    """

[Gankra]

MVP implemented by astral-sh/ruff#21550