moved the draggable node collection inside the editor and attached it to a panel component inside the editor.
also modified the css by creating seperate classes for the draggable nodes inside the ui element
ref: N25B-114
changed to startNode file to be a general file for custom node types, and created a custom type for the data property of StartNode.
BREAKING: renamed StartNode.tsx to NodeDefinitions.tsx
ref: N25B-114