Add a test for passing Intl.Locale objects to Intl.getCanonicalLocales().

Add tests for branding checks in Intl.Locale.prototype members.

Implementation Contributions: Creating initial empty dir for receiving "upstreamed" test material via automaton

Intl: Update language subtag data to "IANA language subtag registry, file date 2018-04-23"

Date.parse breathing test, time value maximum range test

Add tests for the names of getters on Intl.Locale.prototype.

Various additions to the Intl.Locale test coverage.

Add a test for Locale#{minimize,maximize}.

Add Object.prototype.toString tests for BigInt.

fix: comparing typeof expression

Reported by André Bargull in
<https://bugzilla.mozilla.org/show_bug.cgi?id=1464758>.

Add a test for pluralrules.resolvedOptions().pluralCategories.

Check that JSON.stringify works with BigInt objects from other realms

Implementation Contributions: Creating initial empty dir for receiving "upstreamed" test material via automaton

This is based on André Bargull's test case in
<https://bugzilla.mozilla.org/show_bug.cgi?id=1464757>.

Add tests for LineContinuation in StringLiteral

Adding prefixed string to compare with BigInt

Formalize asynchronous failure conditions

Previously, the error message generated by failed asynchronous tests was
generic and underspecified. Improve the format and explicitly document
it in project's interpreting guidelines.

There's a lot of work like this to do, but not enough time in the day to reach it all.

https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry

Improve and extend the tests for ApplyOptionsToTag.

Add some more Locale tests.