update: use vue-demi again to add compatability to vue2

* add vite.config.app.ts for demo generation

src/components/Nodes/DefaultNode.tsx

@@ -1,6 +1,6 @@
 import Handle from '../../components/Handle';
 import { NodeProps, Position } from '../../types';
-import { defineComponent, PropType } from 'vue';
+import { defineComponent, PropType } from 'vue-demi';
 
 const DefaultNode = defineComponent({
   name: 'DefaultNode',

src/components/Nodes/InputNode.tsx

@@ -1,6 +1,6 @@
 import Handle from '../../components/Handle';
 import { NodeProps, Position } from '../../types';
-import { defineComponent, PropType } from 'vue';
+import { defineComponent, PropType } from 'vue-demi';
 
 const InputNode = defineComponent({
   name: 'InputNode',

src/components/Nodes/OutputNode.tsx

@@ -1,6 +1,6 @@
 import Handle from '../../components/Handle';
 import { NodeProps, Position } from '../../types';
-import { defineComponent, PropType } from 'vue';
+import { defineComponent, PropType } from 'vue-demi';
 
 const OutputNode = defineComponent({
   name: 'OutputNode',

src/components/Nodes/wrapNode.tsx

@@ -1,5 +1,5 @@
 import { Node, WrapNodeProps } from '../../types';
-import { computed, CSSProperties, defineComponent, onMounted, provide, ref } from 'vue';
+import { computed, CSSProperties, defineComponent, onMounted, provide, ref } from 'vue-demi';
 import store from '../../store';
 
 export default (NodeComponent: any) => {