Docstrings for arraymodule (#2276)

* start to docstrings for arraymodule

* incorporating toms edits, overriding mypy error...

* fix attrs

* Update src/zarr/core/array.py

Co-authored-by: Sanket Verma <svsanketverma5@gmail.com>

* fix store -> storage

* remove properties from asyncarray docstring

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Co-authored-by: Sanket Verma <svsanketverma5@gmail.com>
Co-authored-by: Joe Hamman <joe@earthmover.io>