Example added: Graph Input from User

[amanchhaparia]

This PR intends to add an example to take a graph input from user.

[meshtag]

Thanks for your work!
What I had in mind for initial design was a comprehensive C++ interface which can accept graphs in all general ways supported by a uniform generic backend which will be used/handled generically in all lowering passes (graph algorithms) of graph dialect.

Feel free to express your ideas about the generic backend capable of all possible interconversions from the C++ user interface.

[amanchhaparia]

Understood your implementation strategy @meshtag!
As a initial impression in my mind I think we can interconvert the graphs into adjacency matrix ie in 2D matrix and can convert it to 1D array as required by the MemRef backend, also it will provide a easy access of the elements while implementing our graph algorithms but its downside is maybe that it is not the most space efficient way.

[meshtag]

Can you please provide some basic code snippets to make sure we are on the same page.

[meshtag]

What is the status of this PR? @amanchhaparia