Link Directly to Cats Package in ScalaDoc

[stephen-lazaro]

This resolves #2005 providing link directly to the cats package in the ScalaDoc.

Rider: Fix some Scala source links in microSite sources that were killed when Contravariant and Invariant were moved out of functor package.

[codecov-io]

Codecov Report

Merging #2050 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #2050   +/-   ##
======================================
  Coverage      95%     95%           
======================================
  Files         311     311           
  Lines        5266    5266           
  Branches      131     131           
======================================
  Hits         5003    5003           
  Misses        263     263

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[LukaJCB]

Ah this is great, thanks! :)

[kailuowang]

Thanks very much!