chore: add socket.io-parser to peerDependencies

This should (at least in theory) fix sync issues for the
`socket.io-adapter` package, which is imported by both the `socket.io`
and `@socket.io/postgres-adapter` packages:

- `[email protected]` should resolve `socket.io-adapter@~2.4.0`
- `[email protected]` should resolve `socket.io-adapter@~2.5.0`

Author: darrachequesne

package-lock.json

@@ -22,8 +22,10 @@
     "@msgpack/msgpack": "~2.8.0",
     "@types/pg": "^8.6.6",
     "debug": "~4.3.4",
-    "pg": "^8.9.0",
-    "socket.io-adapter": "~2.5.2"
+    "pg": "^8.9.0"
+  },
+  "peerDependencies": {
+    "socket.io-adapter": "^2.4.0"
   },
   "devDependencies": {
     "@types/expect.js": "^0.3.29",