Javascript implementation of Binary Heap

[rovilay]

I will like to open a PR for the implementation of Binary Heaps in javascript.

[oyekanmiayo]

Sounds good, I appreciate you volunteering to do this!

We need the following:

• A .md doc explaining the internals of a Heap. Read here to see templates. You can also view sample .md files explaining other data structures throughout the repo.
• A .js file implementing a heap. The file should include sample cases using the implementation. The implementation should also be as generic as possible (i.e. it should be able to store any object type if js allows). Read here for more details.

As you prepare this PR, remember that you must be thorough in your explanations. Everything you write should be understandable. Furthermore, your implementation must use good coding principles (e.g. good variable and method names) and handle edge cases, if any.

I'll review when you're done.

PS: We might find more things to adjust as we go on, so, please be patient through the process.