Import Regex and String Highlighting from Atom

[bscan]

The Raku syntax highlighting is currently taken from the Atom extension here: https://github.com/Raku/atom-language-perl6/. This is also the syntax that powers Github, so is an important repo. Currently, I've only ported the core syntax and not the regex syntax or quoting files. For example, see the following highlighting in github. Vscode does not highlight \d. I assume this would be straightforward to incorporate.

$foo ~~ /Foo\d+bar/;