Proposal: Allow testing when creating a lib project using `init-lib`

[LowByteFox]

Currently, creating lib project using init-lib doesn't provide a way for users to test C3 libraries, a current solution is to create such project.json:

{
    "dependency-search-paths": [".."], /* somehow this works */
    "dependencies": ["name"],
    "test-sources": [ "test/**" ],
    "targets": {
        "foo": { /* a blank target */
            "type": "executable"
        }
    }
}