Better document the use of Heaps with Dynamic Array as Store

[MathewColin]

Fix issue 18333: binaryHeap documentation inadequately describes slice store invalidation

https://issues.dlang.org/show_bug.cgi?id=18333

[dlang-bot]

Thanks for your pull request and interest in making D better, @MathewColin! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
• My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

---

If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment.

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	18333	normal	binaryHeap documentation inadequately describes slice store invalidation

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#8677"

[dkorpel]

Can you please move the new test after the normal example? It's confusing to start with examples of unusual behavior before examples of usual behavior.

[dkorpel]

Suggested change

	/* Internal representation of Binary Heap tree */
	// Internal representation of Binary Heap tree

I suggest using the same comment style as the other example

[MathewColin]

Sure, I will move the example and also change the comment style.