Describe the bug

context
When using the extension on FIPS-enabled systems, hashlib.md5 fails (update_css_js:70) due to security reasons.

expectation
The hashing should work, independently of FIPS being enabled or not.

bug
The following exception is encountered instead:

Extension error (sphinx_design.extension):
Handler <function update_css_js at 0x7f44aa9b9280> for event 'builder-inited' threw an exception (exception: [digital envelope routines] unsupported)

problem
This is a problem for users generating documentation on these systems.

solutions
Changing the algorithm, or adding usedforsecurity=Flag kwarg seems to solve the issue.

hash = hashlib.md5(content.encode("utf8"), usedforsecurity=False).hexdigest()

or

hash = hashlib.sha256(content.encode("utf8")).hexdigest()

Reproduce the bug

1. Enable FIPS on your system
2. Try to generate documentation using sphinx-design
3. Generation fails

List your environment

Standard python-3.9.