build: tsify isolated_renderer/init (#24496)

filenames.auto.gni

@@ -174,7 +174,7 @@ auto_filenames = {
   ]
 
   isolated_bundle_deps = [
-    "lib/isolated_renderer/init.js",
+    "lib/isolated_renderer/init.ts",
     "lib/renderer/web-view/web-view-constants.ts",
     "lib/renderer/web-view/web-view-element.ts",
     "package.json",

typings/internal-ambient.d.ts

@@ -1,4 +1,6 @@
 declare var internalBinding: any;
+declare var nodeProcess: any;
+declare var isolatedWorld: any;
 declare var binding: { get: (name: string) => any; process: NodeJS.Process; createPreloadScript: (src: string) => Function };
 
 declare const BUILDFLAG: (flag: boolean) => boolean;