Reflect changes in GB 18030-2022

[achristensen07]

https://encoding.spec.whatwg.org/index-gb18030.txt contains 18 code points that have been changed by GB 18030-2022. We should probably update.

[domenic]

Related: #27 #57. It's not clear whether web browsers want to update these, or leave legacy encodings forever-unchanged.

[litherum]

We, at least, definitely want to update (in fact, we already did). The definition of this encoding has been updated upstream. There needs to be a consistent behavior between the web browser on a platform and native apps on the platform. As the adage goes, "the future is longer than the past" and there will be more content produced with the new mappings than there is existing content. We can't just close our eyes and hope that all authors use UTF-8, especially when there are laws requiring that ~all products sold in certain places must conform.

[hsivonen]

@litherum Did WebKit implement Unicode Technical Committee recommendation on this topic?

[litherum]

Yes.

[achristensen07]

We ended up moving away from that recommendation and going with the exact GB 18030-2022 mappings instead.