ES2022 Arbitrary module namespace names

[robatwilliams]

Supported by the plugin - https://eslint-community.github.io/eslint-plugin-es-x/rules/no-arbitrary-module-namespace-names.html

Support data is waiting on mdn/browser-compat-data#18152

So this couldn't be done as part of #44

[robatwilliams]

Spec came from tc39/ecma262#2154. Seems to be about alignment rather than a feature people wanted.

I'm not sure why anyone would ever want to use arbitrary string literals for import and export names.

I don't think it's worth implementing this for the sake of completeness alone, so closing. Comment if you think it'd be useful.