Hugo server API to programmatically tell hugo to reload browser

Once hugo server is running an API to instruct the server to refresh programmatically would be nice. As a flag in hugo server maybe when enabled would execute commands to the running server.

When modifying css / a full site rebuild isn’t needed and for large sites can take a few seconds. To speed this up if we could communicate with the server and signal it to refresh the page we could copy statics using 3rd party tools directly to public and then instruct hugo to reload the browser.

We use livereload,js to do browser reloads. That library uses websocket to send commands to the browser, so the API for the browser reload part is kind of there already.