* First commit for back-to-top component

* Added css styles for component and floating variant

* Implemented floating behaviour and fixed lots of issues in intial implementation

* Fixed bugs and implemented some new features. Added react version.

* Implemented Ken's comments

* Removed unneccessory condition

* Reverted siteConfig version which is unncessory

* Component: vf-back-to-top refinements (#1493)

Looking good, thanks

Co-authored-by: Nitin Jadhav <nitin@ebi.ac.uk>
Co-authored-by: Ken Hawkins <khawkins98@gmail.com>