Incomplete steps in "Other systems" section of readme

[ADayn]

Readme states:

2. Create binary for your system:

   pyinstaller --onefile --add-data="img/*;img/" --name="ElegooNeptuneThumbnails-Prusa" elegoo_neptune_thumbnails.py
   

I received the following error:

I fixed it by changing the ; to a : as so:

pyinstaller --onefile --add-data="img/*:img/" --name="ElegooNeptuneThumbnails-Prusa" elegoo_neptune_thumbnails.py

Since this section is meant for non-windows users, it would be helpful if it was mentioned that you'll need to use the colon instead of a semicolon for Mac and Linux.

Also, since you're encouraging people to create a new environment, it should note that the environment should be de-activated after completion.