Add timeout to benchmark solution runs

[rbergen]

Description

I've found that on certain systems/in certain situations, benchmark runs can get stuck for reasons that are unclear. This adds a timeout for each of the solution runs kicked off during the benchmark.

The default timeout is 10 minutes, this can be changed by a new make variable that's also been added to the documentation.

Contributing requirements

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

[rbergen]

Merging after out-of-band review by @davepl.