Feature: Community registry listing

[mathisloge]

i think it would be a good feature if there was a way to list external registries and their ports. I would suggest that these repositories are explicitly added to a list (after checking for quality), which is then regularly searched for ports. And this will increase the visibility significantly. I think there will be some high quality external registries in the future and it would be a pity if they are hard to find by users and there will be some issues of the form in the main vcpkg repository which could be reduced by that.

[autoantwort]

And then also list them at the browse packages site.