Renaming namespaces.

[axelsrz]

This pull request updates the documentation and codebase to reflect a major breaking change in the Python import structure for the Microsoft 365 Agents SDK. All references to the old microsoft.agents import path have been replaced with the new microsoft_agents (using underscores), and the README has been significantly improved to provide clear guidance for users and contributors.

Documentation improvements:

• The README.md has been rewritten to provide a comprehensive overview of the SDK, including package descriptions, usage examples, environment requirements, and code style guidelines. It also highlights the breaking change in the import structure and provides migration instructions.

Migration to new import structure:

• All type annotations and references in model docstrings across files such as activity.py, adaptive_card_invoke_value.py, animation_card.py, and attachment_info.py have been updated from microsoft.agents to microsoft_agents to match the new import path. [1] [2] [3] [4] [5] [6] [7]