add editor config

.editorconfig

@@ -0,0 +1,20 @@
+# http://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# [*.{js,json}]
+[*]
+indent_style = space
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true # doesn't work yet
+insert_final_newline = true # doesn't work yet
+
+[{package.json,*.yml}]
+indent_style = space
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false