Updated OCaml solutions to fix issue (#958)

[gkpotter]

Description

Updated OCaml solutions to use Dune and the latest version of OCaml to fix #958.

Contributing requirements

• [x] I read the contribution guidelines in CONTRIBUTING.md.
• [x] I placed my solution in the correct solution folder.
• [x] I added a README.md with the right badge(s).
• [x] I added a Dockerfile that builds and runs my solution.
• [x] I selected drag-race as the target branch.
• [x] All code herein is licensed compatible with BSD-3.

[rbergen]

@gkpotter Thank you so much! I'm currently running CI on this, which I already know will yield some complaints from Hadolint, our Dockerfile linter. Please let me know if you're ok with addressing those, or if you'd like me to take care of that for you - which will require me to update your main branch.

Correction: CI actually fails because the base images you refer to are untagged - I forgot Hadolint marks this as an error instead of a warning. The "latest" version of the primeimages/ocaml image is 5.1, for the alpine image that would be 3.19.

[gkpotter]

Glad I could help keep this project up to date!