Add STATICFILES_STORAGE with compressor support

[Andrew-Chen-Wang]

Fixes #2739

Description

COMPRESSOR_STORAGE should be set to STATICFILES_STORAGE if not using whitenoise and using something like AWS S3.

Rationale

Compressor cache is stored in the AWS bucket in a separate file structure. For example, without this PR, the files would not have an ACL of public-read:

- CACHE
- static
- media

With this PR:

- static
    - CACHE
- media

The static files storage is set to S3, but the utils (in cookiecutter.project_slug.utils.storages) are set up only for the original collectstatic command, not for compressor support. Thus, compressor would store stuff inside its own directory that did not have public-read.

Use case(s) / visualization(s)

Allow compressor directory of CACHE to be publicly viewable in storage buckets.

[Andrew-Chen-Wang]

You can view this implementation at https://github.com/Donate-Anything/Donate-Anything and view the current website at https://donate-anything.org/. Posting this comment to double check that the files are actually publicly available and the listed project structure from the initial comment is correct.

(I keep getting some favicon.ico error when accessing the admin. I will file a new issue for that, too, although it doesn't happen... often to say the least. I'm not entirely sure why this happens since Sentry doesn't pick up on it but my email logging does).

[browniebroke]

Thanks again @Andrew-Chen-Wang, this is a nice one to fix!