This release adds runeset.ordinalMatch. When this matches the slice,
it returns the ordinal value of the match in the set. For example, "c"
in "abcde" returns 2. A non-match returns null.
runeset.serialize(writer, private, name) writes the RuneSet to writer
as Zig source code. Pass .public for pub and .private otherwise.
The last argument becomes the name of the constant.