feat: add check for protector and enforced pnet

fix: update protector config and tests
docs: add private network info to the readme
test: fix an issue with config

src/index.js

@@ -75,6 +75,13 @@ class Node extends EventEmitter {
       })
     }
 
+    // Attach private network protector
+    if (this._modules.connProtector) {
+      this._switch.protector = this._modules.connProtector
+    } else if (process.env.LIBP2P_FORCE_PNET) {
+      throw new Error('Private network is enforced, but no protector was provided')
+    }
+
     // dht provided components (peerRouting, contentRouting, dht)
     if (this._config.EXPERIMENTAL.dht) {
       const DHT = this._modules.dht