Add "What was this made for" section to README explaining original purpose and expanded use cases

[Copilot]

Added a new section to the README that clearly explains the original motivation behind revect and its expanded applications:

Changes Made

• Added "🎯 What was this made for?" section that explains:
  • Original purpose: Recalling articles and blog posts read in the past without remembering the exact title or content
  • Expanded realization: Useful for shared and persistent memory for teams and individuals across many AI tools

Context

The section provides important context for users about:

• Why revect was originally built (finding previously read content with semantic search)
• How its usefulness has expanded beyond individual article recall to team collaboration and multi-AI tool integration
• Maintains the existing friendly, emoji-rich tone of the README

The addition is minimal (6 lines) and strategically placed after the main tagline to provide immediate context about the tool's purpose and evolution.

Fixes #73.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.