Add `<option/>` tag helper

- #1423
- see earlier commits for prerequisites
Could we make this attribute match the Html5 specs and have it be a boolean attribute?

`<option selected>Mango</option>` < --- Selected
`<option>Bananas</option>` <-- Attribute is absent to denote not selected

In this case we'd have to change this to be a boolean value and we can omit it if it is false.