Update README with Ubuntu command to install python3-pil (InfiniTimeOrg#143)

* Added Ubuntu/Debian command to install python3-pil package in readme

Build may fail without that command on Ubuntu/Debian

* cleanup

Author: fgiaimo

README.md

@@ -73,8 +73,15 @@ pip install wheel Pillow
 
 Optionally, depending on your distro, it may also serve the Pip package as official native installation packages:
 
+On Ubuntu/Debian 
+
+```sh
+sudo apt install python3-pil
+```
+
+On OpenSUSE (Tumbleweed) 
+
 ```sh
-# OpenSUSE Tumbleweed
 sudo zypper install python311-Pillow
 ```