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 #374 (f77cbbb) into master (1a04527) will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #374   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files           2       2           
  Lines           7       7           
======================================
  Misses          7       7           

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[codecov]

Codecov Report

Merging #374 (c688201) into master (286d37d) will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #374   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files           2       2           
  Lines           7       7           
======================================
  Misses          7       7           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 286d37d...c688201. Read the comment docs.

[davidjoy]

Is this good to go? If so, feel free to merge it.

[e0d]

@adamstankiewicz still make sense to merge?

[arbrandes]

This is stale: we already have browserslist config in there.