Added all types from python-data-model which can be hashable

[sindhujapagadala]

THIS IS THE PR FOR THE ISSUE #15
->Added new file: docs/hashable_types.md

Documented the following:

->Definition and concept of hashable objects

->List of built-in hashable types (int, float, str, tuple, etc.)

->Notes on exceptions (e.g., tuples with unhashable elements, readonly memoryview)

->Code snippet demonstrating how to test hashability in Python

->Included links to relevant sections of the official Python documentation