install requires python3.9 to be successful, please update readme

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I struggled for quite a few hours trying to get through the pip3 install -r requirements.txt process.

I used three different distros (raspberry PI OS, ubuntu 20.04 LTS and 22.04) but many of the packages failed.

Using 3.9 still had some failures but they were more manageable. Like needing to install cargo for rust type of things.

edited for grammer

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When pip3 install -r requirements.txt was running it failed part way through as Cargo was required for the build of one of the components that was developed in Rust.

I did end up using a venv for utilizing python3.9 like this:

# Add the deadsnakes repository
me@mydevice:~$ sudo add-apt-repository ppa:deadsnakes/ppa

# Update package lists
me@mydevice:~$ sudo apt update

# Install Python 3.9
me@mydevice:~$ sudo apt install python3.9

# Install the venv package for Python 3.9
me@mydevice:~$ sudo apt install python3.9-venv

# Make a folder for venv virtual environments
me@mydevice:~$ mkdir ~/.venvs

# Create a new venv virtual environment with Python 3.9 in it
me@mydevice:~$ python3.9 -m venv ~/.venvs/my-venv-name

# Activate the new venv
me@mydevice:~$ source ~/.venvs/my-venv-name/bin/activate
(my-venv-name) me@mydevice:~$