Loosen up the death grip on #19 with `switch`

* `switch` is designed to handle multiple logic cases since ES3 and forward.
* There is no requirement for the prior restrictions in any of the styleguides currently mentioned in #19
* Noted that curly braces can be used for code folding, otherwise they are mostly useless imho and as far as I know
* Added `expressionNth` to the sample with a simple fall through.
* GMs requirement of adding a comment for fallthroughs seems rather tautological since this is how the statement has been in the C family of languages and all of its derivatives for many decades.

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Unless I'm missing something entirely the prior restriction was/is "ludicrous"... I am open to read any missed reasoning why this was initially drafted into the STYLEGUIDE.md and why we would want to prevent a set of logic paths from being used with a core statement.

See also:
* https://github.com/OpenUserJs/OpenUserJS.org/commit/0263c797d323cdf76be9cd6f11093903ea250b69#commitcomment-6905688 from ~2 days ago which went out to all admins with no response... so bringing it front and center here with a sooner label since there has been some time to think about this already.

> Our project also uses client-side javascript and therefore the style guide should apply to that as well.

I'll take that as:

> Do you want a server side mention in this sentence?

... a yes.... Doing momentarily.