initial doc commit

[jhamman]

This PR adds project documentation to this repo. There are four main doc types with the following planned pages:

TUTORIALS

• Quick start (install trace package and explore data/models) (@jhamman writes first draft, @orianac reviews)

HOW-TO Guides

• Run the v0 workflow (@jhamman writes first draft, @orianac reviews)
• run the viirs fire mask workflow (@jhamman writes first draft, @orianac reviews)
• V1 steps (@orianac writes first draft, @tcchiao reviews)
  • process glas data
  • generate biomass training data
  • train biomass model
  • run biomass inference
  • post-process biomass predictions

Conceptual Guides

• forest emissions (motivation / overview)
• v0 method description (done for climatetrace)
• v1 method description (done for climatetrace)
• wishlist / roadmap / cookbook

Reference

• API (@jhamman writes first draft, @tcchiao reviews)
• Workflows (@jhamman writes first draft, @tcchiao reviews)

Most docs are currently blank. As we add content, let's check off the boxes above.

@freeman-lab / @katamartin - as the content evolves here, we'll want some help setting up the doc site.