Update docs about pyhton requirements

[latot]

• rgee version: Git
• R version: 4.4.2
• Operating System: Ubuntu Noble

Hi, ee_install needs some libraries to works, in one hand when the function fails is not descriptive, going deeper on it I found ee_install_create_pyenv needs sudo apt install python3-venv python3-pip python3-dev.

I imagine the minimum is pip + venv be available on the user, I think would be nice add this on the README before run ee_install.

Thx!