Enable pushing WIT interfaces via CI

It should be possible to publish a WIT interface from the `component-docs` repo automatically when a certain CI workflow is run.

This *will likely* require the following:

1. Adding `bytecodealliance/component-docs` to the [`docs:adder` package](https://github.com/orgs/bytecodealliance/packages/container/package/docs%2Fadder) list of allowed repositories
2. Creating a CI job that pushes versions of the docs/adder WIT (using the built-in `github.token`)
3. Ensure that we're running `wkg publish` on the textual WIT directory (*not* a built component implementation) -- we should be able to get a minimal WIT-only component