Branding and copy editing changes to the Apicurio Studio docs

[EricWittmann]

Mostly this is branding of Apicurio vs. APICurio. And also making sure that Apicurio Studio is used throughout, to disambiguate it from other Apicurio projects (e.g. Registry). Also maybe one or two typo fixes.

That said, the documentation doesn't mention that you can add the x-kuadrant extension without switching to the full Source tab. The implication I think is that editing the Source directly is required. But users can use the Add Extension dialog instead, which I would argue is a little easier. However, that dialog does require JSON instead of YAML:

I'd be happy to contribute relevant changes if desired. I wasn't sure if the documentation was written this way because it was the preferred way to make the change, or if the Add Extension dialog wasn't discovered by the author. :)

[david-martin]

I'd be happy to contribute relevant changes if desired

That would be awesome @EricWittmann Thanks.
I didn't add it as I wasn't aware it could be done that way.
That's a nice handy shortcut

[EricWittmann]

OK great. Do you want to merge this first or shall I just update this PR with the proposed change?

[david-martin]

We can hold this pr while you make the updates here

[jasonmadigan]

@EricWittmann thanks a lot! I'd be happy to merge these edits right away. Feel free to send along another PR when you get some time for more improvements!

[jasonmadigan]

Will trigger a docs rebuild afterwards.

[EricWittmann]

Yep! This is still on my to-do list. 😀