Transition docs from RST to Markdown

Problem to Solve

Currently the docs for the cli are in RST. This isn't a format used inside of other GitLab projects so our knowledge and support to continue publishing and editing is limited.

Proposal

We should convert the docs to Markdown so that it's easier for more people to contribute.

Additional Questions

Where are we going to store the docs?
Where are we going to publish the docs?
Do we need docs in the main GitLab repo?

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