Keymap-drawer workflow

[urob]

Leveraging the new nix-based workspace, I have added a workflow recipe for parsing and drawing the base.keymap file using keymap-drawer.

The workflow is automated using just draw, which parses the keymap using keymap parse, then does some custom post-processing using yq, and finally plot the result using keymap draw.

Huge thanks to @stijnveenman who got the ball rolling on this in #67.

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