BUG: Documentation currently does not show all the subpackages and modules available in atomate2

[AntObi]

Describe the bug

The API reference in the documentation (https://materialsproject.github.io/atomate2/reference/index.html) currently does not show the whole atomate2 API. For example, the CP2K, qchem and forcefields modules cannot be found in the live documentation. New users to atomate2 would only be able to find these within the source code in the GitHub repository.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://materialsproject.github.io/atomate2/reference/index.html
2. See that there are missing modules in the API reference

Provide any example files that are needed to reproduce the error,
especially if the bug pertains to parsing of a file.

Expected behavior

The expected behavior should be that all the modules should be shown in the API reference as shown on the right in the screenshot above

I've created PR #850 to solve this problem.