Vcpkg support

What would you like Renovate to be able to do?

Vcpkg is a dependency manager for C++ projects. It's still in the early stages, but it's backed by Microsoft, and is likely to be widely used.

Currently vcpkg doesn't have support for versioning, but there is currently an RFC open at microsoft/vcpkg#11758. The format of vcpkg.json is likely to be:

{
    "name": "project", 
    "version": "1.0.0",
    "version-scheme": "semver",
    "dependencies": [
        { "name": "zlib", "version": "1.2.11" },
        { "name": "rapidjson", "version": "2020-02-08", "version-scheme": "date" }]
}

There are more complex examples in the PR, including minimum versions, overrides, and exclusions.

Did you already have any implementation ideas?

Are there any workarounds or alternative ideas you've tried to avoid needing this feature?

Also need to wait for registry support to be complete microsoft/vcpkg#13038

Is this a feature you'd be interested in implementing yourself?

Yes, whenever the RFC is complete.