Move addon events into its own story file

[tmeasday]

A pretty simple change to refactor the events stories out of index.stories.js. Seems to make sense.

[tmeasday]

Tests seem to be broken?

[igor-dv]

@tmeasday, looks like you need to update the snapshots

[codecov]

Codecov Report

Merging #2502 into release/3.3 will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           release/3.3    #2502   +/-   ##
============================================
  Coverage        19.51%   19.51%           
============================================
  Files              386      386           
  Lines             8707     8707           
  Branches           945      962   +17     
============================================
  Hits              1699     1699           
+ Misses            6292     6260   -32     
- Partials           716      748   +32

Impacted Files	Coverage Δ
app/react/src/server/utils.js	0% <0%> (-53.58%)	⬇️
addons/actions/src/lib/types/nan/index.js	29.41% <0%> (ø)	⬆️
addons/actions/src/lib/retrocycle.js	34.09% <0%> (ø)	⬆️
addons/links/src/react/components/link.js	16.66% <0%> (ø)	⬆️
...s/actions/src/lib/types/function/createFunction.js	26.66% <0%> (ø)	⬆️
addons/graphql/src/components/FullScreen/index.js	0% <0%> (ø)	⬆️
addons/knobs/src/components/types/Boolean.js	11.62% <0%> (ø)	⬆️
addons/knobs/src/components/types/Select.js	7.93% <0%> (ø)	⬆️
addons/info/src/components/PropTable.js	29.78% <0%> (ø)	⬆️
addons/actions/src/lib/util/muteProperty.js	14.28% <0%> (ø)	⬆️
... and 67 more

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[ndelangen]

Thanks, great work! 🙇