note:
  ┌─ test.html:1:1
  │
1 │ this is a tag: <h1>test</h1>
  │ ^^^^^^          ^^       ^^ end tag
  │ │               │
  │ │               start tag
  │ attr value
2 │
3 │ tags can have attributes: <div id = foobar>
  │                                ^^ attr name