.com/*matches HTTPS URLs only at "github.com", with any URL path and URL query string. Check out WebExtensions Match Pattern for more examples.
X-Slapdash-Hooks. For example, in NodeJS this can look like:
Access-Control-Expose-Headersto the list of custom hooks that you want to expose. This ensures Slapdash can access
X-Slapdash-Hookswhen making a request to your endpoint.