Added heap data structure in DSA

[jency1]

Pull Request

Description

Added heap data structure in DSA section.

@jfmartinz Please review and merge this PR.

Closes #1574

Type of change

• [x] Adding a new Resource
• [x] Adding a new Category
• [x] Documentation enhancement or fixes
• [x] Website enhancement or fixes

Checklist:

• [x] I read carefully CONTRIBUTING.md
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation