should initialized props in new element

[huodoushigemi]

This helps frameworks such as Vue to detect element props

https://vuejs.org/guide/extras/web-components.html#passing-dom-properties

e.g

const elem = new TestElem();

expect('name' in elem).toBe(true)

[huodoushigemi]

@ryansolid

[huodoushigemi]

🎃

Hey, buddy, this change has passed the test