Add missing docs for functions & props in v12

[peterkogo]

Props, hooks and components

• update Node type (handles, width, height, origin, ..)
• update Edge type (selectable, ..)
• useHandleConnections check return type
• useNodesData check return type (waiting for PR #3929)
• <ReactFlow /> updates
  • colorMode prop
  • viewport prop
  • onViewportChange handler
  • onDelete handler
  • onBeforeDelete handler
  • nodeDragThreshold default value update
  • create new type OnNodesChange and OnEdgesChange and use that for the props list
• check return type of deleteElements
• add patternClassName prop to Background
• add useConnection hook
• add ViewportPortal
• NodeProps -> posX/posY is now called positionAbsoluteX/positionAbsoluteY
• check type of applyNodeChange / applyEdgeChange (are generics being used and explained?)
• check types of useNodes, useNodesState, useEdgesState, applyNodeChange, onInit, applyEdgeChanges , MiniMapProps (are generics being used and explained?)
• document OnNodesChange and OnEdgesChange with detailed descriptions (needs input)

General

• check custom edge component types
• check if nodeInternals is used somewhere - replace with nodeLookup
• check node change events -> "reset" event was replaced with "replace" event
• check if old package name is used
• check if node.positionAbsolute is being used -> replace with node.computed.positionAbsolute
• check if node updates are done with mutations like node.hidden = true; return node
• fix MultiConnectionLine example
• fix EasyConnect example (waiting for #3954)
• fix Add Node On Edge Drop example
• fix touchdevice example
• fix Dagre Tree example
• documente updateNode
• improve useReactFlow doc (needs input)
• add useStore typing to guide
• Solve generics
• viewport (todo)

xyflow/internal#1