addon-options: Make shortcuts in storybook optional

[PunitGr]

Issue: #3196

What I did

I've added an option for enabling/disabling keyboard shortcuts.

How to test

One can try this feature by updating the storybook config.js as:

setOptions({
    ...
    enableShortcuts: false, // true by default
})

This will disable the shortcuts.

[Hypnosphi]

Should we remove shortcuts help button and popup when shortcuts are disabled?

[PunitGr]

Yeah, that makes sense to disable it. Or we can add a text saying that shortcuts have been disabled.

[codecov]

Codecov Report

Merging #3237 into master will decrease coverage by 0.04%.
The diff coverage is 10%.

@@            Coverage Diff             @@
##           master    #3237      +/-   ##
==========================================
- Coverage    35.9%   35.86%   -0.05%     
==========================================
  Files         440      440              
  Lines        9669     9682      +13     
  Branches      904      912       +8     
==========================================
  Hits         3472     3472              
+ Misses       5626     5625       -1     
- Partials      571      585      +14

Impacted Files	Coverage Δ
lib/ui/src/modules/shortcuts/index.js	0% <ø> (ø)	⬆️
lib/ui/src/modules/shortcuts/actions/shortcuts.js	18.84% <0%> (-3.58%)	⬇️
...i/src/modules/ui/components/stories_panel/index.js	21.66% <10%> (ø)	⬆️
.../src/modules/ui/components/stories_panel/header.js	28.57% <50%> (-1.06%)	⬇️
lib/ui/src/modules/ui/containers/stories_panel.js	26.31% <50%> (-0.72%)	⬇️
app/polymer/src/server/utils.js	0% <0%> (-100%)	⬇️
addons/jest/src/hoc/provideJestResult.js	0% <0%> (ø)	⬆️
... and 68 more

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[PunitGr]

Hey @Hypnosphi, Removed the shortcut help button when enableShortcuts: false.

[Hypnosphi]

typo: objectOf

But it's actually not needed here, it should be just shape