Adds typecasting, primitives, variable name, and fixes issue #32

[Tristan-Raz]

Enhanced Variable Declaration Section:
Added details on valid variable naming conventions in Java, including rules and the use of camelCase.
Included an explanation of how Java automatically allocates memory for primitive types, clarifying why operations on them are fast.

Added Primitive Type Casting:
Introduced explanations and code examples for both implicit (widening) and explicit (narrowing) casting between primitive types like int and double.

Added New Section for Class Type Casting:
Created a new subsection titled "Type Casting with Classes (Objects)" to explain casting within an inheritance hierarchy.
Uses a simple Animal/Dog example to demonstrate upcasting (subclass to superclass) and downcasting (superclass to subclass).
Introduces the instanceof operator as a best practice for performing safe downcasts and avoiding ClassCastException.

Removes subsection of IO as Logan is moving that to a separate section.

[pearcej]

@Tristan-Raz What happened to the Input / Output / Scanner subsection?

[Tristan-Raz]

@pearcej Logan is making a section about Input/ Output/ Scanner and libraries. He asked me to remove it so that he would not create a merge conflict. Do you want me to add it back?

[pearcej]

@pearcej Logan is making a section about Input/ Output/ Scanner and libraries. He asked me to remove it so that he would not create a merge conflict. Do you want me to add it back?

Sorry. I missed that comment in the original description. Let's wait until I get his pull request.