C++: Add C++ analysis team to CODEOWNERS

[jbj]

We previously removed our entry because the notifications got too noisy, but we agreed recently in the C++ analysis team to try adding an entry with just the analysis team and only in the public repository.

[geoffw0]

I'm finding it much easier to track new github pull requests since someone pointed out the #github-ql Slack channel to me. I forget what @dave-bartolomeo and @rdmarsh2 said they'd prefer.

[rdmarsh2]

I'm happy either way.

[dave-bartolomeo]

I think I'd prefer the codeowners file, because the on US time, I mostly see #github-ql as a big list of all the PRs submitted from Europe the night before, rather than an as-it-happens feed of what PRs are being created. It's easier for me to filter email than it is to deal with this in Slack. That said, I would get by just fine just using Slack if that's what everybody else wants.

[geoffw0]

OK, sounds like we should merge this and see how we get on with it.