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 #495 (a6b81cd) into master (3da88dd) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #495   +/-   ##
=======================================
  Coverage   60.37%   60.37%           
=======================================
  Files          45       45           
  Lines         795      795           
  Branches      146      146           
=======================================
  Hits          480      480           
  Misses        305      305           
  Partials       10       10           

---

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 7948812...a6b81cd. Read the comment docs.

[codecov]

Codecov Report

Merging #495 (dc7f492) into master (fa602f5) will not change coverage.
The diff coverage is n/a.

❗ Current head dc7f492 differs from pull request most recent head 17c420e. Consider uploading reports for the commit 17c420e to get more accurate results

@@           Coverage Diff           @@
##           master     #495   +/-   ##
=======================================
  Coverage   60.37%   60.37%           
=======================================
  Files          45       45           
  Lines         795      795           
  Branches      146      146           
=======================================
  Hits          480      480           
  Misses        305      305           
  Partials       10       10           

---

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 fa602f5...17c420e. Read the comment docs.

[davidjoy]

Hmm, can/should these PRs also remove es-check? Is there are reason not to?

[Jawayria]

Hmm, can/should these PRs also remove es-check? Is there are reason not to?

@adamstankiewicz might have a better idea about it.

[adamstankiewicz]

@Jawayria @davidjoy Let's keep es-check, but check for ES6 rather than ES5. Validating against ES6 will help keep some guardrails in place to let us know when we use the latest JS syntax features, but our Babel configuration doesn't transpile it down to ES6 as expected.

I think it was a bit premature to assume we'd remove it earlier when I opened these PRs 😄

[Jawayria]

@Jawayria @davidjoy Let's keep es-check, but check for ES6 rather than ES5. Validating against ES6 will help keep some guardrails in place to let us know when we use the latest JS syntax features, but our Babel configuration doesn't transpile it down to ES6 as expected.

I think it was a bit premature to assume we'd remove it earlier when I opened these PRs 😄

@adamstankiewicz es6 checks fail on browserslist-config PRs but these tests are passing if a new PR is created against master branch.

[jsnwesson]

Browserslist-config was added in a more recent PR. #649