Document deployment on Raspberry Pi

[sansaid]

This was done as a workaround until ARM target image is fixed.

• Needed to manually install Python 3.9 (with these instructions): https://itheo.nl/install-python-3-9-on-raspberry-pi/
• Built a virtual environment: python3.9 -m venv <path>
• Activated virtual environment
• Installed requirements.txt
• Set envvar TG_API_TOKEN
• Ran: nohup python bot.py > logs 2>&1 & (to let it run in the background)
• To check on the nohup process: ps xw | grep bot