Clarify Ruff installation requirement before running lint commands

[Tithi234]

Hi 👋,

In the "Running Code Style Checks" section of the README, contributors are instructed to run:

However, it may not be immediately clear to new contributors that Ruff needs to be installed first.

Would it be helpful to briefly mention how to install Ruff (for example via pip or from requirements.txt) before running these commands?

Happy to open a PR with a suggested clarification if this sounds reasonable.

Thanks!