note:
   ┌─ test.html:3:17
   │
 3 │ Here is a tag: <strong >very cool</strong>
   │                 ^^^^^^             ^^^^^^ EndTag
   │                 │
   │                 StartTag
 4 │
 5 │ Tags can have attributes: <div id = foo >...</div>
   │                                ^^   ^^^ attribute value
   │                                │
   │                                attribute name
 6 │
 7 │ Attribute values can be quoted: <input name = 'age' type = "number">
   │                                                ^^^          ^^^^^^ in double quotes
   │                                                │
   │                                                in single quotes
 8 │
 9 │ This is malformed < test
   │                    ^ unexpected character: saw ' ' in state TagOpen
10 │
11 │ Characters can be escaped but don't forget the semicolon: &#182
   │                                                               ^ semicolon missing after character reference