fix(ComponentExample): clipboard and active state

[levithomason]

Fixes #2770

This PR is largely copied from v2:

• fix copy direct link clipboard
• fix example active state when clicking code/html/direct and using direct links
• add better hover state style and improve listener performance

[codecov-io]

Codecov Report

Merging #2796 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2796   +/-   ##
=======================================
  Coverage   99.74%   99.74%           
=======================================
  Files         160      160           
  Lines        2762     2762           
=======================================
  Hits         2755     2755           
  Misses          7        7

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[levithomason]

Released in semantic-ui-react@0.80.1.