Add support for dot shorthands

[erikas-taroza]

Updates tree-sitter-dart for the grammar and adds highlighting.

It seems there is still some errors present in the syntax tree, mainly when using a dot shorthand with the const keyword (ex. const .function()) but this will have to be fixed in https://github.com/UserNobody14/tree-sitter-dart

Before:

After:

void main() {
  final MyClass myClass = .new("");
  final MyClass myClass2 = .named("");
  const MyEnum myEnum = .one;
}

class MyClass {
  final String field;

  MyClass(this.field);
  MyClass.named(this.field);
}

enum MyEnum { one, two }

[MrSubidubi]

Thanks for this! Looks good overall, could you please share a quick before/after, please?

[erikas-taroza]

Thanks for this! Looks good overall, could you please share a quick before/after, please?

I have updated the first comment with screenshots.