Add comprehensive documentation and code comments

This commit adds extensive documentation to the Mistral OCR CLI project:

- Add API.md with detailed API response format documentation
- Add CHANGELOG.md to track version changes
- Add CONTRIBUTING.md with guidelines for contributors
- Enhance README.md with more detailed usage examples and troubleshooting
- Add proper docstrings to all Python modules and functions
- Update requirements.txt with development dependencies
- Improve setup.py with better metadata

These changes make the project more accessible to users and contributors.

mistral_ocr/__init__.py

@@ -1 +1,17 @@
-# Mistral OCR Python Package
+"""
+Mistral OCR Python Package
+
+A command-line tool for processing documents with Mistral AI's OCR capabilities.
+This package provides functionality for extracting text and structured content
+from PDF documents and images while preserving the original formatting and layout.
+
+Main components:
+- Client for interacting with the Mistral AI OCR API
+- Commands for processing documents, converting results to Markdown, and more
+- Utilities for handling file operations and formatting
+
+For usage information, see the README.md file or run:
+    mistral-ocr --help
+"""
+
+__version__ = "0.1.0"