[FORK] Update the landing page

[TonyBagnall]

I think we should remove all of this
https://github.com/scikit-time/scikit-time/blob/main/README.md
for now, and just have a simple message "This is a fork of sktime made by previous core developers, and is a work in progress" or something. Any thoughts on that?

[MatthewMiddlehurst]

Will need to keep some stuff, but definitely needs to be reworked for sure.

[MatthewMiddlehurst]

Currently, uses a disclaimer, still needs to be updated with new links.

[TonyBagnall]

I'll close this if no one minds. The landing page is currently stable, and further changes will be more specific than this and relate to name etc, so are in my mind a separate issue.