New `dask-sphinx-theme` is not showing up

[scharlottej13]

I noticed the new dask-sphinx-theme (see https://github.com/dask/community/issues/220) isn't showing up for the dask-ctl docs.

When trying to build locally, I got the following error from dask_config_sphinx_ext:

Exception occurred:
  File "/Users/sarahj/mambaforge/envs/dask-ctl-docs/lib/python3.8/site-packages/dask_sphinx_theme/ext/dask_config_sphinx_ext.py", line 35, in run
    config = config[k]
KeyError: 'ctl'

@jacobtomlinson any ideas here?

cc @jsignell