Remove IE11 vendor polyfills

[domoscargin]

Partially addresses #2506

[domoscargin]

Gzipped size of minified JS file:

Before: 9.3kB
After: 8kB

A few thoughts:

Intl API

There's some mentions of IE11 in the i18n's check for Plural Rules and Number Format support.

Can we simplify these checks to just look for .supportedLocalesOf and assume we're good on Intl and PluralRules/NumberFormat? Or do we need to keep these checks as is? @querkmachine - you probably have thoughts?

edit: see #2621 (comment)

Bits and bobs

There's a coupla things that come up when searching for "IE" (stuff like IE rendering in the template, potentially some html-validate rules, some specific fixes for components, etc.

Not sure we have anywhere to start logging these things to tackle as we go about the work of updating things?

Documentation

Should we just remove the polyfilling sections of our documentation?

[domoscargin]

Comment about non-vendored polyfills here: #2621 (comment)

[36degrees]

There's some mentions of IE11 in the i18n's check for Plural Rules and Number Format support.

Can we simplify these checks to just look for .supportedLocalesOf and assume we're good on Intl and PluralRules/NumberFormat? Or do we need to keep these checks as is? @querkmachine - you probably have thoughts?

I find browsersl.ist really useful for looking at the intersection of support for these features and ES6 modules. For example, here's the browsers that support ES6 modules but don't support Intl.PluralRules.

Because that list isn't empty, we probably do need to keep the checks around for now. However, we do have an issue to remove the fallback 'polyfill' in a future 5.x release – we'll still need to keep the checks, but we can just fall back to the 'other' translation in the few older browsers that don't support it.

There's a coupla things that come up when searching for "IE" (stuff like IE rendering in the template, potentially some html-validate rules, some specific fixes for components, etc.

Not sure we have anywhere to start logging these things to tackle as we go about the work of updating things?

These are great catches! I reckon add comments to #2621 for now, like you have already for the various JS APIs? They seem unrelated to the polyfill changes in this PR.

[domoscargin]

@colinrotherham I've updated polyfilling documentation and linked to #3722

[colinrotherham]

@colinrotherham I've updated polyfilling documentation and linked to #3722

Nice, thanks @domoscargin. Keeps the git blame history going