Setup `mypy' for static type checking

.mypy.ini

@@ -0,0 +1,13 @@
+[mypy]
+strict_optional = False
+ignore_missing_imports = True
+install_types = True
+non_interactive = True
+show_error_codes = True
+exclude = (?x)(
+    src/interface/desktop/main_window.py
+    | src/interface/desktop/file_browser.py
+    | src/interface/desktop/system_tray.py
+    | build/*
+    | tests/*
+  )