no luck installing by following the instructions (solved)

On my Linux Mint 20 machine, I did

```sh
sudo apt install libffi-dev libssl-dev
pip install warcprox
```

However, this did not result in an executable being installed. After some soul-searching I then did

```sh
pip3 install --user warcprox
```

which worked as expected. I want to politely suggest an update to the README.