Refactor types into type declaration files

[NathanWEdwards]

Type definitions are scattered all throughout the repository. Types should be refined and placed within a common directory.

Requirement criteria:

• A suitable folder is made for type declarations of all kinds
• A README is created for guidance on defining types and interfaces
• A link to the newly created README on defining types and interfaces has a hyperlink reference within the project's root README
• Types declarations are defined within a type definition file having a .d.ts extension
• Interfaces, classes, and methods are refactored to accommodate type definitions
• Variables are typed
• Method signatures are bestowed with generic typing where appropriate