Intent to ship: Well-Formed Unicode Strings

[Yoshi Cheng-Hao Huang]

As of Firefox 119, I intend to turn on Well-Formed Unicode Strings (JS) by default

Bug to turn on by default:

https://bugzilla.mozilla.org/show_bug.cgi?id=1850755

Standard:

https://tc39.es/ecma262/#sec-string.prototype.iswellformed

https://tc39.es/ecma262/#sec-string.prototype.towellformed

The feature was previously discussed in "Intent to prototype: Well-Formed Unicode Strings"

https://groups.google.com/a/mozilla.org/g/dev-platform/c/lJercpdK6VY/m/swRCS6N3AQAJ