[golang] Create vanity for go.wrpc

[ricochet]

Since we believe wRPC will be a foundational mutli-stakeholder project, there's a good chance it may be moved to another organization. We can keep from modifying our code if a transition occurs by providing a vanity url.

Create a vanity URL with github pages to go.wrpc.io.

The go work is currently in a subdir at github.com/wrpc/wrpc/go. If we use github pages, we need to test if we can host an index.html using modgen so that go.wrpc.io -> wrpc.github.io/wrpc/go