[Documentation] [Readme] Add initial documentation to your README.md

[MaximRouiller]

As a user, I would like to see how AzureTableStorageHelper would help me simplify my code.

I would also like to know what kind of assumptions this library is taking (CreateIfNotExists calls, etc.)

Adding proper documentation and sample code to your README.md would help people decide whether they want to use your library or not.

[leeenglestone]

Yep. I deffo should do this.