Features:
- Sticks section headers to their parent's div edges top or bottom on overflow
- All heights of sections, headers, and sidebar are flexible
- Clicking Section title smooth scrolls it to the top
- Supports window resizing
- Matching Webflow UI
- Ticks collapse item, name links to it (Section 2 is collapsed on load)
- Still scrollable if cursor hovers over fixed item by mousewheel capture
- Supports DOM injection (Section 7 is loaded in 2 sec on load)
To-Do:
- Make collapsing/showing section content smooth scroll work in combination with updating the snapped elements on bottom
- Clean code