add additional ws optional dep

Author: feross

package.json

@@ -52,7 +52,8 @@
     "webtorrent-fixtures": "^1.3.0"
   },
   "optionalDependencies": {
-    "bufferutil": "^4.0.0"
+    "bufferutil": "^4.0.0",
+    "utf-8-validate": "^5.0.1"
   },
   "keywords": [
     "bittorrent",