Docs: fix logos display & add babelrc

[Hypnosphi]

Issue:
— "Used by" logos are not displayed on docsite: http://storybooks.netlify.com/
— Docs package don't work without root dependencies (see #2203)

It turns out that it's enough to add an empty .babelrc as gatsby's defaults work OK.

How to test

In project root:

rm -rf node_modules
cd docs
yarn install
yarn dev

[codecov]

Codecov Report

Merging #2585 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2585   +/-   ##
=======================================
  Coverage   32.68%   32.68%           
=======================================
  Files         398      398           
  Lines        8838     8838           
  Branches      947      943    -4     
=======================================
  Hits         2889     2889           
+ Misses       5296     5293    -3     
- Partials      653      656    +3

Impacted Files	Coverage Δ
app/vue/src/server/utils.js	0% <0%> (-53.58%)	⬇️
lib/ui/src/modules/api/actions/api.js	51.85% <0%> (ø)	⬆️
lib/ui/src/libs/withLifecycleDecorator.js	17.14% <0%> (ø)	⬆️
addons/actions/src/lib/reviver.js	58.33% <0%> (ø)	⬆️
addons/a11y/src/components/WrapStory.js	72.09% <0%> (ø)	⬆️
addons/knobs/src/components/PropField.js	10.63% <0%> (ø)	⬆️
lib/ui/src/modules/ui/routes.js	0% <0%> (ø)	⬆️
addons/graphql/src/components/FullScreen/index.js	0% <0%> (ø)	⬆️
addons/a11y/src/components/Report/Rules.js	0% <0%> (ø)	⬆️
addons/jest/src/hoc/provideJestResult.js	0% <0%> (ø)	⬆️
... and 48 more

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