fix(eio): add @types/ws as dependency (#5458)

Since engine.io@6.6.5, the generated .d.ts files import types from "ws"
(WebSocket, PerMessageDeflateOptions), but @types/ws was not declared as
a dependency. This causes TypeScript compilation errors for consumers
who do not have @types/ws installed.

This follows the existing pattern where @types/cors and @types/node are
already listed as dependencies.

Related: #5437

Author: Not-Sarthak

package-lock.json

@@ -33,6 +33,7 @@
   "dependencies": {
     "@types/cors": "^2.8.12",
     "@types/node": ">=10.0.0",
+    "@types/ws": "^8.5.12",
     "accepts": "~1.3.4",
     "base64id": "2.0.0",
     "cookie": "~0.7.2",