Added intro to loading and working with maps

[JBorrow]

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 39.17%. Comparing base (71f4ff5) to head (afc5617). Report is 2 commits behind head on docs.

Additional details and impacted files

@@           Coverage Diff           @@
##             docs     #304   +/-   ##
=======================================
  Coverage   39.17%   39.17%           
=======================================
  Files          32       32           
  Lines       10776    10776           
=======================================
  Hits         4221     4221           
  Misses       6555     6555           

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