Feat: add support for rendering named slots (#887)

[ferm10n]

No description provided.

[lmiller1990]

Any chance you can add a unit test? If not I might be able to do it. Didn't realize named slots wasn't supported.

[ferm10n]

I plan on it, just haven't had the time to focus on it yet. #887 was closed too so my PR might not be needed. I'll check tomorrow

[ferm10n]

So it looks like e604f1c fixes this. I like that solution a lot better than mine lol, so I'm closing.
However there seems to be some trouble when using following the example on https://vuejs.org/v2/guide/components-slots.html#Named-Slots, which uses the template element for named slots.

JSDOM does not serialize template contents, in accordance with the spec.

@eddyerburgh do you have any input on this, with regards to handling template elements?

[eddyerburgh]

Can you give me an example in code of the problem, and raise a new issue so I can track it

[ferm10n]

https://codesandbox.io/s/p4mmxj9mx (Learning how to use this tool, I didn't know how to pull in the latest version that is on the dev branch here)

I'm not entirely sure what should happen here to be honest, but I do imagine that it shouldn't be blank.

Here's the reason why you'd get <template></template>. I misspoke earlier, parse5 is the cause, which is used by JSDOM.