move docs

[mzgubic]

The index page is empty, this moves the usage to the index page

[codecov]

Codecov Report

Merging #19 (bffae94) into main (12b8875) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #19   +/-   ##
=======================================
  Coverage   95.09%   95.09%           
=======================================
  Files           4        4           
  Lines         102      102           
=======================================
  Hits           97       97           
  Misses          5        5           

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