Fix accessibility warnings

[Hypnosphi]

Issue: Some elements of storybook UI are unusable with keyboard. They have click handlers and even tabindex attributes, but no keyboard handlers.

What I did

Used <button type="button"/> in those cases. It sometimes required a bit of style resetting

How to test

Navigate to following elements with tab and hit Enter key:
— tab headings in addons panel
— color picker in addon-knobs
— "Show info" button in addon-info

[codecov]

Codecov Report

Merging #2270 into master will increase coverage by <.01%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #2270      +/-   ##
==========================================
+ Coverage   22.16%   22.16%   +<.01%     
==========================================
  Files         268      268              
  Lines        5884     5883       -1     
  Branches      711      714       +3     
==========================================
  Hits         1304     1304              
+ Misses       4060     4018      -42     
- Partials      520      561      +41

Impacted Files	Coverage Δ
...mments/src/manager/components/CommentItem/style.js	0% <ø> (ø)	⬆️
...mments/src/manager/components/CommentItem/index.js	0% <ø> (ø)	⬆️
addons/knobs/src/components/types/Color.js	8.21% <0%> (+0.11%)	⬆️
...b/ui/src/modules/ui/components/down_panel/index.js	96% <100%> (ø)	⬆️
addons/info/src/components/Story.js	76.19% <100%> (ø)	⬆️
app/vue/src/server/config/babel.js	0% <0%> (-100%)	⬇️
app/vue/src/server/babel_config.js	0% <0%> (-77.42%)	⬇️
app/vue/src/server/utils.js	0% <0%> (-53.58%)	⬇️
lib/ui/src/modules/api/configs/init_api.js	40.47% <0%> (ø)	⬆️
addons/info/src/components/Node.js	39.13% <0%> (ø)	⬆️
... and 29 more

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