add a basic .editorconfig, fixes #2734

.editorconfig

@@ -0,0 +1,11 @@
+# EditorConfig is awesome: http://EditorConfig.org
+
+root = true
+
+[*]
+end_of_line = lf
+charset = utf-8
+indent_style = space
+indent_size = 4
+insert_final_newline = true
+trim_trailing_whitespace = true