Microcassette case

This is a case for a single audio [microcassette](https://en.wikipedia.org/wiki/Microcassette) (as used in dictation recorders and answering machines, not a ["compact" cassette](https://en.wikipedia.org/wiki/Cassette_tape) for music).

Present features (compared to a standard commercially-made case):

* It snaps shut.
* It locks the tape reels in position to prevent unwinding due to vibration.

Absent features:

* It probably will not comfortably fit a [J-card](https://en.wikipedia.org/wiki/J-card) unless enlarged, and even if it were it would not be transparent like a molded polycarbonate case.
* It does not have ridges/recess to assist in pulling open the case, but I find that the printed plastic is rough enough not to need them much.

Possible improvements that could be made:

* Compact cassette version — once I have a cassette to test fit with.
* Window to reveal labeling, at the cost of less dust protection.
* Make the .scad Customizer-compatible for tweaks.

Als