Feat: When an hx-ext tag is used in the current or a parent element enable autocompletion based on it

[itepastra]

Some extensions, like websockets make use of some extra tags. When the extension is active (I.e. this element or a parent element has the hx-ext=extension attribute) we could also include the extension tags and attributes

an example:

<div hx-ext="ws">
    <div ws- #autocomplete to ws-send for example
</div>
<div ws- #does not autocomplete

I get it if this isn't added too soon, the parsing has to allow it first.