adopt editorconfig

.editorconfig

@@ -0,0 +1,12 @@
+# https://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[{*.py,setup.cfg}]
+indent_size = 4