ENH: `Styler.set_sticky` for maintaining index and column headers in HTML frame
- [x] closes #29072

This allows you to quickly make the index and/or column headers stick in place when scrolling in HTML.
Additional args allow the control of subselecting specific multiindex levels and controlling the width /or height of the sticking elements.

https://user-images.githubusercontent.com/24256554/122395757-99017700-cf77-11eb-93f0-f3c401afca4e.mov


