add aspell to CI

[johrstrom]

#4122 and all the work on the documentation seems to indicate we need some guardrails to make sure we write documents that have correct spelling.

This ticket is to add aspell to the CI (tests.yml?) so we can be sure any documentation we have has correct spelling. Don't know if this applies to code - but seems like it should if it can.

[johrstrom]

This is being fixed in #4671.

[moffatsadeghi]

Notes from GitHub review meeting:

Mentioned there's an open PR for this
Recalled it was breaking fixtures
Clarified the open PR is about adding a dependency for an open source project that checks spelling
Noted it would check spelling during CI on pull requests
Conclusion:
Issue will be closed as it's being addressed in an open PR
Will be included in version 4.1 tracking