Finalize 1st draft of types and structs, add docs

[vlandau]

Title says it all.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (main@de0e7e1). Click here to learn what that means.
The diff coverage is n/a.

@@          Coverage Diff           @@
##             main      #1   +/-   ##
======================================
  Coverage        ?   0.00%           
======================================
  Files           ?       1           
  Lines           ?      13           
  Branches        ?       0           
======================================
  Hits            ?       0           
  Misses          ?      13           
  Partials        ?       0           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update de0e7e1...3840ea3. Read the comment docs.