[Getting Started] Make first page more welcoming

[JacksonKearl]

With #116570 we open to the first section when no items have been completed. This means the first screen new users see is:

This could be more welcoming... on Codespaces on the other hand the first screen will be:

Which seems reasonable to me.

[JacksonKearl]

(cc @digitarald for possible content updates, @misolori for design tweaks)

[digitarald]

I had #116580 filed for this but can close as dupe.

[JacksonKearl]

Oh sorry didn't see that one. This is a bit different now because we only ever open the first category (Codespaces / Quick Setup). I'm fine with closing either one as duplicate.

[miguelsolorio]

I was thinking maybe we could adjust the layout and add a title + move the more button, but only for when this opens as the landing page:

[digitarald]

@misolori I like context it adds. Might be also useful if the header could stick around across index and each sections. Depending on viewport size, it could responsively shrink/grow.

[JacksonKearl]

Now that we've changed the header, this doesn't really make sense. Going to just close this out.