Add Design Patterns Examples

[KnightMode]

First time contributor here, Could i take up the task of adding the below design patterns: 1)Builder 2)Factory 3)Observer

[sulemangit]

Hi, first-time contributor here , can I pick this up will add the implementation for the singleton design pattern

[SiddharthaAnand]

Sure go ahead! Make sure you have the following steps.

1. A generic problem
2. Simple design solution in words in the comments/readme
3. The code
4. Unit test