convert lvgl from submodule to a plain old directory

lib/lvgl/scripts/filetohex.py

@@ -0,0 +1,11 @@
+#!/usr/bin/env python3
+import sys
+
+with open(sys.argv[1], 'r') as file:
+    s = file.read()
+
+b = bytearray()
+b.extend(map(ord, s))
+
+for a in b: print(hex(a), end =", ")
+