... to conform to UTS 18 as mentioned in https://bugs.ruby-lang.org/issues/19417#note-3https://unicode.org/reports/tr18/#word states word should match join_control chars.
It currently does not:
```ruby
[*0x0..0xD799, *0xE000..0x10FFFF].map { |n| n.chr 'utf-8' } => all_chars
all_chars.grep(/\p{join_control}/) => jc
jc.count # => 2
jc.grep(/\p{word}/).count # => 0
```