feat(extensions): most of the extensions implementation, by kdb424

setup.cfg

@@ -22,9 +22,8 @@ per-file-ignores =
 # multiple spaces after commas in lists (for grid alignment), and put
 # your imports in whatever order you want
 	user_keymaps/**/*.py: E131,F401,E501,E241,E131,BLK100,I003
+	boards/**/main.py: E131,F401,E501,E241,E131,BLK100
 	tests/test_data/keymaps/**/*.py: F401,E501
-# Forgive me for my RAM hack sins
-	kmk/preload_imports.py: I001,I003,I004,F401
 
 [isort]
 known_standard_library =