[ESC190] Add section on increment and decrement operators

[Youssef-Rachad]

A current blurb exists at the end of Lecture 7 on strings.

A better approach would be to have a section dedicated to increment and decrement operators.

• Describe '++' and '--'
• Explain the subtlety between prefixing and suffixing
• Go crazy with somtheing like '--+++var++--++'
• Give examples related to loops and pointer arithmetic

Goal is to have an easily accessible reference. Separating it also increases granularity.