Min max stack example

[Iinguistics]

Added a stack class example in js & added imported the code into the md file.

[leios]

I do intend to eventually add code to this chapter, so this PR is a good idea in principle; however, I don't know enough JS to say whether this is a good, fundamental implementation of a stack or queue in that language.

right now, my understanding is that this code goes a bit futher to allow for outputing the maximum or minimum element in the stack, which is useful, but not what I was thinking of for this chapter.

[ntindle]

[lang: javascript]