Add Z3D-E621-Convnext as an Interrogator tagging option

[dm18]

adds support for Z3D-E621-Convnext https://huggingface.co/toynya/Z3D-E621-Convnext

[RoelKluin]

Thanks for the PR, it will require some testing. One question, however; what exactly is the reason that this is a separate class?

[dm18]

for tagger/interrogator.py ,
For the new class, ,

Line 669 set tags_path to tags-selected.csv. So it can download, and use tags-selected.csv.

The first couple of tags were showing up in the ratings box, but were not ratings.
Line 819 was changed from 3 to 0
line 824 was changed from 3 to 0.
Which moves the first couple of tags down into the tag box.

Line 671 might need to be set to false.

I didn't know how much modification would be needed. A separate class meant ether class could be modified without any un attended effects to other model. I was not trying to make larger design decisions.