editorconfig: add rst

.editorconfig

@@ -33,3 +33,12 @@ insert_final_newline = true
 indent_style = tab
 indent_size = 4
 max_line_length = 120
+
+# reStructuredText
+[*.rst]
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+indent_style = space
+indent_size = 3
+max_line_length = 120