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/cluster-adapter` packages:

- `socket.io@4.5.0` should resolve `socket.io-adapter@~2.4.0`
- `socket.io@4.6.0` should resolve `socket.io-adapter@~2.5.0`