Self-closing tags arent parsed properly


```
const parse = require('posthtml-parser')
const result = parse("<p> Hello <World/> yes</p>")
console.log(JSON.stringify(result, undefined, 2))
[
  {
    "tag": "p",
    "content": [
      " Hello ",
      {
        "tag": "World",
        "content": [
          " yes"
        ]
      }
    ]
  }
]
```