build(deps): update dependencies

[ylemkimon]

• Flow
  • https://medium.com/flow-type/making-flow-error-suppressions-more-specific-280aa4e3c95c
• Jest
  • jest-serializer-html: Trim diffed HTML and improve serializer test. algolia/jest-serializer-html#17
• Explicitly declare dependencies
• Commit /website/yarn.lock

Closes #2259.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (master@e76857e). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2301   +/-   ##
=========================================
  Coverage          ?   94.76%           
=========================================
  Files             ?       84           
  Lines             ?     5382           
  Branches          ?      943           
=========================================
  Hits              ?     5100           
  Misses            ?      258           
  Partials          ?       24           

Flag	Coverage Δ
#screenshotter	88.48% <ø> (?)
#test	88.64% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
contrib/render-a11y-string/render-a11y-string.js	89.18% <ø> (ø)
src/Parser.js	96.85% <ø> (ø)
src/buildMathML.js	98.14% <ø> (ø)
src/defineEnvironment.js	100.00% <ø> (ø)
src/functions/environment.js	100.00% <ø> (ø)
src/functions/op.js	98.75% <ø> (ø)
src/parseNode.js	80.00% <ø> (ø)
src/functions/horizBrace.js	100.00% <0.00%> (ø)
src/unicodeScripts.js	100.00% <0.00%> (ø)
src/functions/operatorname.js	96.15% <0.00%> (ø)
... and 81 more

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[ronkok]

This looks good to me. These are welcome upgrades.