Add .prettierrc to the template

[harshnilve28]

Description:
Add a .prettierrc file with { "singleQuote": true } to enforce single quotes in Prettier formatting across editors like VSCode. This matches the project’s pre-commit style and avoids formatting mismatches.
I’m a beginner contributor—sorry for any mistakes! Still trying to learn and grow.

Checklist:

• No tests needed for this config change.
• Documentation update not required but can be added later if desired.

Rationale:
Ensures consistent code style and better experience for contributors, especially beginners. Fixes formatting issues described in issue #4512.