add editor config

.editorconfig

@@ -0,0 +1,15 @@
+root = true
+
+[*]
+# Change these settings to your own preference
+indent_style = space
+indent_size = 2
+
+# We recommend you to keep these unchanged
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.md]
+trim_trailing_whitespace = false