feat: Document static file mount gotcha

[ofipify]

Pull Request Checklist

• [x] Make sure to read the contributor guide here.
• [x] Make sure you are making a pull request against the main branch.
• [x] Make sure your pull request title matches the requested format.
• [x] Make sure to lint, type-check, and run unit and API tests.

Description

Document the gotcha and workaround for static file mounts being dependent on order of operations (see #55)

I've also added an example and a test for that example in case this behaviour ever changes.

[alexschimpf]

@ofipify Can you merge in the latest main branch? That should fix the issue with the tests. Also please see the linter failures as well.

[ofipify]

Done. Didn't realise I could run make lint locally.