Add support for the v flag

[vbudovski]

Thank you for this excellent tool! I came across the issue below.

What is the problem?

The flag v is not supported. https://tc39.es/ecma262/multipage/text-processing.html#sec-get-regexp.prototype.flags

[makenowjust]

Thank you for reporting.

I tried to implement it in #378 (See

recheck/modules/resyntax/shared/src/main/scala/codes/quine/labs/resyntax/ast/FlagSet.scala

Lines 56 to 57 in c6359c4

	// `v` (JavaScript)
	unicodeSets: Boolean = false,

), but it is still working in progress. Sorry.