string lib: pattern matching (pcre regex)

[giann]

• [X] Pattern new type: pat pattern = _^hello$_;
• [ ] Allow pattern initialization with a string pat pattern = "^with a string$";

pat methods are:

• [X] pattern.match(str subject) > [str]: Returns the first match and eventual captures
• [X] pattern.matchAll(str subject) > [[str]]: Returns all matches and captures
• [x] pattern.replace(str subject, str replacement) > str: Replaces first match with replacement
• [x] pattern.replaceAll(str subject, str replacement) > str: Replaces all matches with replacement
• [ ] handle named capture

str methods:

• [ ] string.match(pat pattern) > [str]: same as pattern.match
• [ ] string.matchAll(pat pattern) > [str]: same as pattern.matchAll
• [ ] string.replace(pat pattern) > [str]: same as pattern.replace
• [ ] string.replaceAll(pat pattern) > [str]: same as pattern.replaceAll
• [ ] When #54 is done, string.match and pattern.match should return iterators.

[giann]

Use pomsky? https://github.com/rulex-rs/pomsky