Install emmet extension by default

[KyleBarton]

Closes #32713

Release Notes:

• Added the Emmet extension to auto-loaded extensions list

[maxdeviant]

Hmm, I don't think we should do this.

We already have snippet support built-in (correct me if I'm wrong about that, @osiewicz).

But Emmet is a very specific tool that not everyone is going to want out-of-the-box.

[KyleBarton]

@maxdeviant got it - #32713 suggested the goal was feature parity with VS Code, which does auto-install - but do you think it would be better as a suggested extension?

If so, we might need to tweak suggested extensions a bit, since the HashMap datatype suggests that there should be only one suggested extension per file type (and this would overlap with the html extension)

[KyleBarton]

FWIW, I don't see snippets working out of the box right now, but I could be incorrectly testing - I'm not the most familiar with Emmet-style html editing.