Enhance ContentReader with New Formatting Options and Code Refactoring

[supitsdu]

Description

Update ContentReader, Dependencies, and README.md for Enhanced Functionality

Changes Made

• Implemented ContentReader to manage file contents and input streams efficiently.
• Updated dependencies in go.mod to include github.com/gabriel-vasile/mimetype v1.4.4 and github.com/stretchr/testify v1.9.0.
• Enhanced README.md with new features like Mimetype & Codeblock and clarified installation instructions.

Checklist

• [x] Implemented ContentReader for file content management.
• [x] Updated dependencies in go.mod.
• [x] Enhanced README.md with new features and installation instructions.
• [x] Verified changes with appropriate tests.