Test docs as part of CI

🚀 Feature

Test every code snippet in the project documentation to keep it always up to date with code changes.

Motivation

Documentation can become easily obsolete, especially in fast moving projects as Thunder.

For example, the code in this section of documentation is obsolete and generates an error when executed:

Traceback (most recent call last):
  File "<redacted>/example.py", line 5, in <module>
    from thunder.tests.litgpt_model import Config
ModuleNotFoundError: No module named 'thunder.tests'

The reason is that the Config object was moved to another project. Changing the import from from thunder.tests.litgpt_model import Config to from litgpt import Config fixes the issue.

Pitch

CI should execute code snippets in documentation and catch errors as above.

Alternatives

Additional context

The issue was discussed with @tfogal et al who requested to report it here.

Start with the documentation section linked in the issue and reproduce its outdated import error. Then identify how the project's documentation snippets are organized and where CI configuration lives. Done means the documentation code snippets are executed in CI and failures such as the missing thunder.tests module are reported.