MDN to in-tree migration tool

Writing docs for Firefox's in-tree source docs can be time consuming and difficult. Making the process of contributing to the in-tree docs an enjoyable experience is very important so that more people would contribute to the source docs. Implementing a renderer at review phase would be one of the steps toward that goal since reviewers don’t have to build the docs locally and just access s3 to review the diff and make the code-test-commit-review cycle shorter.

With MDN de-prioritizing build and workflow docs, we need a suitable replacement for all of Firefox's contribution and workflow documentation. Documentation has been moved to in-tree which offers great advantages such as that it can be updated along with the source. Migrating documentation from MDN is a tedious process done manually since there are no mechanisms to make the migration easier. With the help of a web crawler and pandoc, we could make a script to use the crawler to extract all the documentation from the MDN site and convert it to Rst files that can be added to the in-tree docs.