Add CI check that configs.md is up-to-date

[andygrove]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
We have a partially automated solution for keeping the configuration guide up-to-date.

When new configs are added in config.rs, we can run cargo run --bin print_config_docs to generate the markdown for the user guide and then manually copy it into docs/source/user-guide/configs.md.

We do not have CI checks to make sure that this is being done when new configs are added.

Describe the solution you'd like
In CI:

• Run cargo run --bin print_config_docs
• Check that there are no modified files

Describe alternatives you've considered
None

Additional context
None

[mvanschellebeeck]

Hey @andygrove, first time contributor here - happy to take this one!

Just to sanity check my thinking - does as run of ./dev/update_config_docs.sh and then a new job that runs a diff in workflows/dev.yml make sense here?