build: use shared browserslist config

[adamstankiewicz]

• Removes custom browserslist configuration in favor of using a shared configuration.
• Removes is-es5 check in CI since ES5 was only needed for IE 11 support which is dropped. The supported browsers defined by the shared configuration all natively support ES6.

This change reduces the resultant asset bundle size.

[codecov-commenter]

Codecov Report

Merging #545 (f19d22b) into master (a18daec) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #545   +/-   ##
=======================================
  Coverage   40.78%   40.78%           
=======================================
  Files         107      107           
  Lines        2236     2236           
  Branches      604      604           
=======================================
  Hits          912      912           
  Misses       1240     1240           
  Partials       84       84           

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[codecov]

Codecov Report

Merging #545 (4d8151a) into master (c39fd33) will not change coverage.
The diff coverage is n/a.

❗ Current head 4d8151a differs from pull request most recent head ba5456b. Consider uploading reports for the commit ba5456b to get more accurate results

@@           Coverage Diff           @@
##           master     #545   +/-   ##
=======================================
  Coverage   39.53%   39.53%           
=======================================
  Files         106      106           
  Lines        2188     2188           
  Branches      582      582           
=======================================
  Hits          865      865           
  Misses       1238     1238           
  Partials       85       85           

---

Continue to review full report at Codecov.

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[davidjoy]

Is this good to go? If so we can get it merged.

[abdullahwaheed]

duplicates #607. closing this