Improper use of STORAGES['sass_processor']['ROOT'] settings for Django >= 4.2

[miguelsmatos]

Foremost, thank you for making this library available, really appreciate all the work that goes into it.

I seem to have found two issues related with changes made with the setting SASS_PROCESSOR_ROOT for Django>=4.2:

1. The README.md seems to suggest that the output directory can be configured for Django>=4.2 with STORAGES['sass_processor']['ROOT']. However, looks like we're using STORAGES['sass_processor']['OPTIONS']['ROOT'] in sass_processor/storage.py.
2. On the same sass_processor/storage.py, the dictionary storage_options=sass_processor_storage.get("OPTIONS") seems to be modified in place; this results in a conflict when SassFileStorage is not a singleton – which it is not – as we pop ROOT. This could be easily fixed by replacing the same line with storage_options = copy.deepcopy(sass_processor_storage.get("OPTIONS") or {}).

I am happy to submit a pull request if you are able to confirm that this is indeed an issue, and which is the design intention for this setting (or its path).