message: Parse BlockString
  Adds the BlockString rule to the String regex parser.
  I noticed there are no unit tests for the parser in this repo, so tested with
diff: @@ -42,7 +42,7 @@ export const LexRules = {
  Number: /^-?(?:0|(?:[1-9][0-9]*))(?:\.[0-9]*)?(?:[eE][+-]?[0-9]+)?/,
  // Note the closing quote is made optional as an IDE experience improvment.
  - String: /^"(?:[^"\\]|\\(?:"|\/|\\|b|f|n|r|t|u[0-9a-fA-F]{4}))*"?/,
  + String: /^(?:"""(?:\\"""|[^"]|"[^"]|""[^"])*(?:""")?|"(?:[^"\\]|\\(?:"|\/|\\|b|f|n|r|t|u[0-9a-fA-F]{4}))*"?)/,
  // Comments consume entire lines.
  Comment: /^#.*/,
  