docs(TreeSelect): add custom content demo (#4272)

src/tree-select/demo/data.en-US.ts

@@ -0,0 +1,66 @@
+const group1 = [
+  {
+    text: 'Delaware',
+    id: 1
+  },
+  {
+    text: 'Florida',
+    id: 2
+  },
+  {
+    text: 'Georqia',
+    id: 3,
+    disabled: true
+  },
+  {
+    text: 'Indiana',
+    id: 4
+  }
+];
+
+const group2 = [
+  {
+    text: 'Alabama',
+    id: 5
+  },
+  {
+    text: 'Kansas',
+    id: 6
+  },
+  {
+    text: 'Louisiana',
+    id: 7
+  },
+  {
+    text: 'Texas',
+    id: 8
+  }
+];
+
+const group3 = [
+  {
+    text: 'Alabama',
+    id: 9
+  },
+  {
+    text: 'Kansas',
+    id: 10
+  }
+];
+
+
+export const enUSData = [
+  {
+    text: 'Group 1',
+    children: group1
+  },
+  {
+    text: 'Group 2',
+    children: group2
+  },
+  {
+    text: 'Group 3',
+    disabled: true,
+    children: group3
+  }
+];