Feat: Add VariablePickerMenuPlugin to select variables in the prompt text box by menu #4764 (#4765)

### What problem does this PR solve?

Feat: Add VariablePickerMenuPlugin to select variables in the prompt
text box by menu #4764

### Type of change


- [x] New Feature (non-breaking change which adds functionality)

web/src/components/prompt-editor/variable-node.tsx

@@ -0,0 +1,70 @@
+import i18n from '@/locales/config';
+import { BeginId } from '@/pages/flow/constant';
+import { DecoratorNode, LexicalNode, NodeKey } from 'lexical';
+import { ReactNode } from 'react';
+const prefix = BeginId + '@';
+
+export class VariableNode extends DecoratorNode<ReactNode> {
+  __value: string;
+  __label: string;
+
+  static getType(): string {
+    return 'variable';
+  }
+
+  static clone(node: VariableNode): VariableNode {
+    return new VariableNode(node.__value, node.__label, node.__key);
+  }
+
+  constructor(value: string, label: string, key?: NodeKey) {
+    super(key);
+    this.__value = value;
+    this.__label = label;
+  }
+
+  createDOM(): HTMLElement {
+    const dom = document.createElement('span');
+    dom.className = 'mr-1';
+
+    return dom;
+  }
+
+  updateDOM(): false {
+    return false;
+  }
+
+  decorate(): ReactNode {
+    let content: ReactNode = (
+      <span className="text-blue-600">{this.__label}</span>
+    );
+    if (this.__value.startsWith(prefix)) {
+      content = (
+        <div>
+          <span>{i18n.t(`flow.begin`)}</span> / {content}
+        </div>
+      );
+    }
+    return (
+      <div className="bg-gray-200 dark:bg-gray-400 text-primary inline-flex items-center rounded-md px-2 py-0">
+        {content}
+      </div>
+    );
+  }
+
+  getTextContent(): string {
+    return `{${this.__value}}`;
+  }
+}
+
+export function $createVariableNode(
+  value: string,
+  label: string,
+): VariableNode {
+  return new VariableNode(value, label);
+}
+
+export function $isVariableNode(
+  node: LexicalNode | null | undefined,
+): node is VariableNode {
+  return node instanceof VariableNode;
+}