added a type for defaultNodeData, this can house common data that all nodes should have. the other types can build on this defaultData. Also added an endNode and phaseNode to NodeDefinitions.tsx, together with a nodeData type for each new node type.
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
Added ReactFlow to dependencies (@xyflow/react).
Added a basic reactflow template to test functionality of reactFlow and to build the visual programming UI on top of.
ref: N25B-114