Improve Installation / Colab notebook

Improve Installation Stability

🙌 Thanks to @Nickfagiano help with debugging.

• #487 update installation to work with MacOS BigSur
• #487 improve setup with Conda path guard
• #487 lock atari-py version to 0.2.6 for safety

Google Colab/Jupyter

🙌 Thanks to @piosif97 for helping.

• added instruction for Google Colab/Jupyter
• example Colab notebook

Windows setup

🙌 Thanks to @vladimirnitu and @steindaian for providing the PDF.

• added Windows setup instruction