Multithreaded Ruby Solution using Ractor

[darnellbrawner]

Description

Takes advantage of multi-core systems using Ractor ruby's actor model framework. https://ruby-doc.org/core-3.0.0/Ractor.html

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]

Hi @darnellbrawner, I see you're now contributing the multithreaded implementation(s) you announced earlier. You have now structured these additions as two fully independent solutions. This means that for each of your three implementations a separate Docker image is built and run when the benchmark is executed, which is not very efficient.

May I ask you to structure your PR to add these new implementations to your existing PrimeRuby/solution_2 solution instead? That solution can then run all three implementations in sequence, in one docker run. It also means we can merge without requiring a review from the second maintainer.