Document `autoapisummary`

[astrojuanlu]

I'm trying to move a docs project from sphinx.autosummary to sphinx-autoapi, so I'm trying to understand whether I can translate the .. autosummary directives with .. autoapisummary. However, the latter is not documented. It's defined here:

sphinx-autoapi/autoapi/directives.py

Lines 12 to 13 in 85739d5

	class AutoapiSummary(Autosummary): # pylint: disable=too-few-public-methods
	"""A version of autosummary that uses static analysis."""