Use isort

[isort](https://isort.readthedocs.io/en/latest/) sorts your Python
imports so you don't have to. This makes sure that imports are always
where they should be and prevents issues like duplicated imports and
merge conflicts. Using pre-commit, this can be done automatically
without any manual steps.

Depends on #9.

main.py

@@ -2,11 +2,10 @@
 import sys
 
 from config import Config
-from lib.library import Catalogue
-from lib.pyShelf import InitFiles
-from lib.pyShelf import BookServer
-from lib.pyShelf import BookDisplay
 from lib.display import Frontend
+from lib.library import Catalogue
+from lib.pyShelf import BookDisplay, BookServer, InitFiles
+
 # sys.path.insert(1, 'lib/')
 
 config = Config()  # Get configuration settings