Mercury

Fixes
- 254 fixes local links navigation

Fixes
- 248, 249, 250

Fixes
- fix cell update index when recomputing notebook in 247 - thank you fryanpan for steps to reproduce

Enhancements
- 195 - add `url_key` to widgets
- 234 automatically detect static notebooks
- 237 add `disabled` and `hidden` arguments
- 166 add a share button
- 242 add chat widget
- 227 add confetti widget

Bug fixes
- 228, 235, 232, 236, 241

Fixes
- (224) fixed problem with exporting slides to PDF

Fixes
Small fixes in auth (219):
- added Membership in Admin Panel
- load welcome message with access rights check