docs: Add detailed Introduction to Agile ChapterAdd agile chapter1

[Krishna-Sah26]

Related Issue

Fixes #18

Description

Added detailed Chapter 1 - Introduction to Agile with:

• What is Agile (with examples)
• Agile Manifesto & 4 Core Values (with explanations)
• 12 Agile Principles (detailed)
• Agile vs Waterfall (with real examples)

Content is beginner-friendly with detailed
explanations and practical examples as suggested
in previous PR feedback.

Type of Change

• Documentation update

Checklist

• My code follows the project structure
• Tested locally
• Linked related issue
• No existing functionality broken

AI Usage

• I have used AI tools (Claude) and reviewed,
  verified all content before submitting

[vercel]

@Krishna-Sah26 is attempting to deploy a commit to the PushkarScripts Team on Vercel.

A member of the Team first needs to authorize it.

[Krishna-Sah26]

Hi @pushkarscripts!

This PR contains only Chapter 1 - Introduction
to Agile with detailed explanations and examples
as per your feedback on PR #24.

The first commit is from the previous PR attempt.
The main changes are in the second commit.

Please review when you get a chance. 🙏

[pushkarscripts]

• Your file structure is flawed. Spend some time and go through the codebase to follow the file structure of the project.
  
• Also, since it is for a single chapter in a series of PRs on a single issue. Replace Fixes # with Related to # in PR description.

Make these changes to be considered for review.