[d3-cloud] Support import syntax (#30479)

* Allow importing from `d3-cloud`

* Modify export to be CommonJS

types/d3-cloud/d3-cloud-tests.ts

@@ -1,3 +1,12 @@
+import d3Cloud = require('./index.d');
+import d3 = require('d3');
+
+// $ExpectType Cloud<Word>
+d3Cloud();
+
+// $ExpectType Cloud<Word>
+d3.layout.cloud();
+
 interface ICompTextSize{
   text:string;
   size:number;

types/d3-cloud/index.d.ts

@@ -5,6 +5,8 @@
 
 import * as d3 from 'd3';
 
+export = d3.layout.cloud;
+
 declare module 'd3' {
     namespace layout {
         export function cloud(): Cloud<cloud.Word>;