v1.4.0: Enable the generation of Markdown docs for Glean metrics and pings (#89)
* Add a second data review to the core.yaml test file
* Add the Markdown outputter and template
This allows to produce human-readable docs
from Glean registry files.
* Add the Kotlin outputter to the translate unit
* Add test coverage for the markdown outputter
* Make flake8 and black happy
* Bonus: remove the double definition of 'description'
* Don't break the table for multiline extra keys description
* Fetch ping information for custom pings from pings.yaml
* Add a disclaimer to the Markdown template
* Bonus: mention that jinja templates are not auto generated
* Remove dead code