- [x] Have you followed the guidelines for contributing? - [x] Have you signed the [CLA](http://www.ubuntu.com/legal/contributors/)? - [x] Have you successfully run `make lint && make test`? --- This PR adds references to [pebble docs](https://documentation.ubuntu.com/pebble/) in the Pebble page inside rockcraft documentation. This page only keeps the information from pebble related to container images and rocks. Additionally, other pages have been modified so when Pebble is mentioned it links to the pebble page. --- See built page here: (waiting CI)