Move static assets from gh-pages branch.

[hexedpackets]

Github lets us publish docs from the /docs folder instead of the gh-pages branch. Moving the documentation into master will reduce friction when we need to update docs along with a code change.

[dmichel1]

nice! +1

[codecov]

Codecov Report

Merging #438 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #438   +/-   ##
=========================================
  Coverage     49.45%   49.45%           
- Complexity     2932     2933    +1     
=========================================
  Files           733      733           
  Lines         20229    20229           
  Branches       1495     1495           
=========================================
  Hits          10005    10005           
  Misses         9724     9724           
  Partials        500      500

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