Set up CompatHelper to check test and docs

[mtfishman]

@lkdvos this sets up CompatHelper to check the test and docs Project.tomls.

I noticed that we don't generally have compat entries for test and docs dependencies, which causes trouble if test or docs dependencies make breaking releases, for example in ITensor/BlockSparseArrays.jl#68. This should make it easier to add compat entries and make sure they stay updated.

I'll merge so I can start testing it out in some other packages.

[lkdvos]

We should perhaps also consider checking if we can make Aqua spit out errors for missing/stale dependencies and/or missing compat entries. I know it does this for the test dependencies if they are defined under the [targets] section of the main Project, but maybe it's also possible to extend that.

[mtfishman]

We should perhaps also consider checking if we can make Aqua spit out errors for missing/stale dependencies and/or missing compat entries. I know it does this for the test dependencies if they are defined under the [targets] section of the main Project, but maybe it's also possible to extend that.

Good suggestion, that would be great to have it is a check in Aqua as well, that would make it easier to fix it more proactively rather than waiting for CompatHelper PRs. Unfortunately I can't seem to find that as an option of Aqua right now.

[mtfishman]

It looks like this works (I ran it manually from https://github.com/ITensor/NamedDimsArrays.jl). Unfortunately it is going to make a lot of PRs because there are a lot of missing compat entries right now.