0.11: add doc redirects

[flying-sheep]

I see locally:

/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_csv.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_elem.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_excel.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_h5ad.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_hdf.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_loom.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_mtx.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_text.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_umi_tools.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.read_zarr.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.sparse_dataset.rst: WARNING: document isn't included in any toctree
/home/phil/Dev/Python/Single Cell/anndata/docs/generated/anndata.write_elem.rst: WARNING: document isn't included in any toctree

after releasing 0.11, we should add redirects: https://readthedocs.com/dashboard/icb-anndata/redirects/