Separate license check for [dev-dependencies] vs [dependencies]

[hrydgard]

Sometimes, it might be interesting to use libraries with release-incompatible licenses in [dev-dependencies]. One example would be dssim, which is licensed under AGPL, and can be useful for comparing graphical output to a reference image while tolerating minor visually-invisible differences. In this case, its license doesn't need to be considered for the final binary release since neither the code nor any of its output will be included in it.

In deny.toml, the interface for this could be to simply have an additional allow-dev section. Like below:

[licenses]
...
allow = ["MIT", "Apache-2.0", "zlib"]
dev-allow = ["GPL", "AGPL"]

dev-allow would implicitly include everything from allow, since I can't really imagine a case where a library would not be OK to use for local tests, but OK in a final binary.

[kazuk]

I wish to add build-allow for [build-dependencies]