Improve MultiChart UI by fixing the Chart selector after scrolling down

[fredericvc]

https://www.loom.com/share/9191847250f249faa3c084c33f4f200e?sid=7b1c78b1-8db7-45a5-bd87-18381a4fcf78

[radu]

Improved.

[fredericvc]

Thanks for the improvement!

Now I realize that on mobile that leaves only a half screen available for charts.

Ideas
1/ upon scrolling down the banners disappears, when scrolling up the banners reappear (in scroll fashion) before the main page (with the charts) scrolls up
2/ smaller fonts, smaller drop downs

[radu]

Improved it slightly