add README note for config flag conflict

Example:
If debug is true and config is false, assets will not be resolved
by sprockets and will fall back to the standard rails public dir
resolution.

In this situation
  `stylesheet_link_tag('application')` will resolve to
  `/stylesheets/application.css` instead of
  `/assets/application.css`

Author: bjallen

README.md

@@ -121,7 +121,7 @@ is not enabled, then we check the environment if compiling is enabled:
 # Production default.
 %i[ manifest ]
 ```
-
+If the resolver list is empty (e.g. if debug is true and compile is false), the standard rails public path resolution will be used.
 
 ## Complementary plugins