Feature Request: Specify a list of submodules to check out

[vyas-n]

As of today, the actions/checkout (v4.1.7) input submodules only allows the following options: true, false, & recursive.

This works for development workloads, but in my case I only need CI to check out 2 submodules out of a list of 12.

I'd like the ability to specify a list of the submodules I want to check out. This is for the goal of reducing the network bandwidth required for my GitHub Actions runner for my repo. (some submodules are huge, and I don't need it for CI).