docs: add contributors appreciation section to README

[SujalMahapatra]

Description

Added a Contributors Appreciation section to the README to recognize and thank community contributors.

Changes Made

• Added a Contributors Appreciation section
• Included a thank-you message for contributors
• Added a contributors image generated from GitHub contributors data
• Maintained the existing README style and formatting

Related Issue

Fixes imDarshanGK#752

Type of change

• Bug fix
• New feature / enhancement
• Documentation update
• Test addition
• Refactor

Checklist

• I have read CONTRIBUTING.md
• My branch is up to date with main
• [] I have run pytest -v and all tests pass
• I have not introduced duplicate issues or features
• My PR title follows the format: feat/fix/docs/test: short description
• [] I have added tests for new features (Level 2 and 3 issues)
• No hardcoded secrets or API keys in my code
• This PR is linked to a GSSoC 2026 issue

Screenshots (if frontend change)

Not applicable — this is a documentation-only change

Test evidence

Not applicable — this is a documentation-only change

pytest -v
# paste output
Not applicable — this is a documentation-only change