editorconfig: add networkmanager.rules style (MR 5070)

This is forked from Alpine. Keep the style to not increase the diff.

.editorconfig

@@ -12,3 +12,8 @@ indent_style = tab
 end_of_line = lf
 trim_trailing_whitespace = true
 insert_final_newline = true
+
+# Forked from Alpine
+[extra-repos/systemd/networkmanager/networkmanager.rules]
+indent_style = space
+indent_size = 4