fix: multiple links next to each other are resolved as single link

[lopo12123]

Trying to fix #34

---

The test case is as follows

final cases = [
  // (raw content, expected)
  ('![link](url)', 0),
  ('[link](url)', 1),
  ('[li\nnk](url)', 0),
  ('[link](u\nrl)', 0),
  ('[li\\]nk](url)', 1),
  ('[link](ur\\)l)', 1),
  ('[link](url)[link2](url2)', 2),
  ('[link](url) [link2](url2)', 2),
];

void main() {
  final reg = RegExp(
    r"(?<!!)\[((?:[^\]\n]|\\\])*)\]\(((?:[^)\n]|\\\))*)\)",
    dotAll: true,
    multiLine: true,
  );

  for (final entry in cases) {
    print(
        "${entry.$1.replaceAll('\n', '\\n')} => ${reg.allMatches(entry.$1).length}/${entry.$2}");
  }
}