Modernization of the Django admin

### Code of Conduct

- [x] I agree to follow Django's Code of Conduct

### Feature Description

Modernizing the Django admin.
I feel that improvements to the UI/UX are needed.

### Problem

Improving the UI/UX of the Django admin.
The backend of the Django admin is also built with older code and has many template tags centered around ChangeList, which I think can be somewhat problematic. However, I believe that what’s more needed is the improvement of the UI/UX rather than the backend.
(The exact scope of modernization may need to be discussed.)

### Request or proposal

proposal

### Additional Details

Among third party Django admin packages, there are already some that have excellent themes.
As an example, here are some packages that personally have designs I prefer.

- https://github.com/unfoldadmin/django-unfold
- https://github.com/farridav/django-jazzmin

### Implementation Suggestions

I feel that making partial UI/UX improvements within the Core is somewhat difficult. While there are good approaches available, in practice it is challenging due to additional work, such as slightly modifying the structure. Moreover, improving only part of the UI can actually feel awkward.

I wonder if it would be possible for Django to provide a public separate package with a UI/UX enhanced admin theme. I believe such a Django admin theme package should prioritize compatibility so that it does not break existing customizations of the Django admin template when applied. It should also adopt the most “Django-like” design in terms of colors, fonts, and overall style.

Finally, it should consider accessibility standards that is, it should be designed for everyone, including those in minority groups.

Merging this into Core is not strictly necessary, and it would be fine to merge later if it gains popularity and poses no significant issues. Therefore, I think it would be possible to offer an improved UI/UX theme without any pressure.