Add "Open in Codepen" button to Treegrid example

[spectranaut]

Adding the open in Codepen button! This involved moving some SVGs and moving some code.

Preview

[carmacleod]

Looks good!

Approving now, even though it can't be merged until the cspell ignore regex is fixed.

@nschonni Is the following regex correct?
"url\\(\"data\\:image/svg\\+xml.*\"\\)[,;]"

[nschonni]

@carmacleod makes sense to me, or the punctuation could possibly be dropped entirely. I was just trying to make sure the regex didn't get to greedy, but maybe that's not really an issue for this

[carmacleod]

Thank-you, @nschonni - I created #1696 to add [,;] to the end of the regex. Good point about probably not needing to be that specific because it's pretty unlikely that anything else will ever match, however I decided to check for the end punctuation anyhow. 😄

I have no idea how to test whether merging 1696 will allow this PR to pass the spell-check. (but I think it should work...)

[mcking65]

Looks great ... this would have been a perfect opportunity to improve how we set aria-current. I think it should be on the link inside the list item, not on the entire list item. Rendering aria-current on a long item is awkward for screen readers. I'll raise a separate issue for that though. I want to get this merged.