Converted all files to TS + Small cleanup to API + new simpler components

Changes

• Added Types for StickyTree, AutoSizedStickyTree
• Added a new component StickyList and AutoSizedStickyList which simplifies the API for those that just want to render a list. See CitiesList.tsx in examples.
• Added examples and Cypress tests - you can run these locally with npm start

Breaking Changes

• defaultRowHeight prop is now just rowHeight
• getChildren receives to node object for the parent, and should now return a node as a prop on the info return, e.g

 const getChildren = (node: MyNodeType, nodeInfo: EnhancedStickyTreeNode<MyNodeType>) => {
 return [
 { 
 isSticky: true,
 node: { id: 'child1', name: 'Child 1' }
 }
 ]
 }

• onRowsRendered props for startNode and endNode are now of type EnhancedStickyTreeNode<TNodeType>
• rowRenderer now receives the node to render that was returned by getChildren, e.g.

 const rowRenderer = ({ node, style }) => {
 return (
 <div className="node-row" style={style} key={node.id}>
 {node.name}
 </div>
 );
 }