Update readthedocs.io documentation

[kviktor]

The linked http://django-imagekit.rtfd.org/ seems out of date, the only available version tag there is 1.1.0 for example, you can see a lot of config options are also missing

https://django-imagekit.readthedocs.io/en/develop/configuration.html
vs
https://github.com/matthewwithanm/django-imagekit/blob/develop/docs/configuration.rst

[vstoykov]

@matthewwithanm for the read the docs I don't have access and can't see what is the issue. Do you have the time to see?

[matthewwithanm]

Weird, I just checked and I don't have access either! @bryanveloso do you remember how we used to do this?

[bryanveloso]

I have no clue, it's been a bit. 🥲 Password manager tells me I have an account at readthedocs, so I'll give that a shot and report back.

[bryanveloso]

"well there's your problem." 🤪

I've sent you both invites to the project.

[kviktor]

This looks a bit wild 😅