Add Google Analytics to documentation

[shaydewael]

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov-io]

Codecov Report

Merging #178 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #178   +/-   ##
=======================================
  Coverage   48.86%   48.86%           
=======================================
  Files           7        7           
  Lines         440      440           
  Branches      120      120           
=======================================
  Hits          215      215           
  Misses        213      213           
  Partials       12       12

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