style: add editor config

Author: aspirantzhang

.editorconfig

@@ -0,0 +1,12 @@
+# http://editorconfig.org
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+
+[*.{json}]
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true