Create an API architecture diagram and Quick Start guide for the ORAS Go library

[FeynmanZhou]

We need to create an API architecture diagram for the ORAS library (ORAS-go, ORAS-py) to illustrate the API function and logic, this will help new folks easily understand the ORAS API capabilities.

ORAS-py has made good examples at user guide and developer guide. So this issue is mainly for ORAS-go.

[Wwwsylvia]

I can take this for oras-go.
I think we can add the below content as the first step:

1. What is oras-go 
	- Short description
2. Get Started 
	- How to import the package
	- Simple End-to-end examples
3. Architecture Diagram
       - Abstractions and APIs

[FeynmanZhou]

@Wwwsylvia This proposal looks good to me. Let's start with this content structure for ORAS-go quick start.

[DishaJain17]

@FeynmanZhou Kindly have a look
https://docs.google.com/document/d/1eylGDc36ohhki_8UaDLKpoDn7Ih_A9SOMKRh8jbEQxc/edit
Please review the attached detailed flowchart without design for your review. Kindly provide feedback , your input is greatly appreciated.
Thanks