CSP Compliance, bring `rangeChanged` to GroupedVirtuoso

Two PRs merged:

• A change which makes the component CSP compliant (#77)
• Port of rangeChanged to the GroupedVirtuoso component variant. (#81)

Fix scrollToIndex regression

The issue was spotted in #75 and was related to changes aimed at making scrollToIndex more resilient.

Fix warnings in React 16.13.0

Virtuoso and GroupedVirtuoso are now functional components. This should not cause any change in the behavior, but if it does - please open an issue!

More fixes for elastic bouncing in Safari

Fixes the problems described in #70 and #72.

Fix elastic bounce in Safari

Contains a fix for #70

A host of new features!

Probably the biggest release since the initial one. New features:

• Initial Index lets you start the list from the middle or from the bottom.
• Prepend Items convenience method for prepending items to the top of the list.
• A range callback lets you track the scrolling changes of the list.
• Stick to bottom lets you build a tail -f like interface easily.
• Scroll Seek Placeholders let you avoid loading data and display placeholders instead when the user scrolls too fast.

Under the hood, scrollToIndex is now more resilient, and handles unexpected item heights.
A new property, maxRangeSize lets you handle huge jagged lists (read more in the API reference).

Share your feedback in the issues section!

Community contributions!

Thanks to the contributors, a few new features were added:

• itemsRendered callback is exposed
• totalListHeightChanged callback is exposed

Documentation for both is available in the site (callback properties).

Server-Side Rendering

Server-side rendering now works for the Virtuoso component. You need to set the initialItemCount property to render some items regardless of the container/item size.

Also, fixed error when setting the VirtuosoGrid totalCount to zero: #24.

New component - VirtuosoGrid

The VirtuosoGrid component displays same sized items in multiple columns.
The layout and item sizing are controlled through CSS class properties, which allows you to use media queries, min-width, percentage, etc.

Check the responsive grid columns example for a sample implementation.

Works in Edge!

Thanks to the reports and PR from @jiggum and @StoicH the library (and the site) now works in MS Edge.

P.S. the library build infrastructure is standing on the shoulders of giants; again, huge thanks to @palmerhq for making tsdx.