💄 Add an app icon

Fix #15

main.py

@@ -1,5 +1,6 @@
 import os
 import sys
+from tkinter import PhotoImage
 
 import customtkinter
 
@@ -16,6 +17,8 @@ def main():
     root = customtkinter.CTk()
     root.title("Drawing Training!")
     root.geometry("300x600")
+    icon = PhotoImage(file="assets/icons/logo-dt.png")
+    root.iconphoto(True, icon)
 
     App(root)