IVS in string searching

[xfq]

In an IVS, when VS and the previous code point are displayed and used, they should be treated as one "character" when displayed. When doing string searching operations, the first code point should be the processing baseline. For example, if two Han characters appear together, such as "龍VS天" (U+9F8D U+E0100 U+5929), searching "龍天" should match the relevant content. If necessary, the browser can also include some preference to config "precise" string searching operations.

Some IVS examples:

• https://xfq.github.io/testing/ivs/ivs.xml (UTF-8)
• https://xfq.github.io/testing/ivs/ivs4gb.xml (GB 18030)

Currently, Blink and WebKit supports this, but Gecko does not.

Maybe we can add it to https://w3c.github.io/string-search/#orthoVariation ?