docs: auto relay example (#795)

* chore: auto relay example

* chore: update examples to use process arguments

* chore: add test setup for node tests and test for auto-relay

* chore: apply suggestions from code review

* chore: do not use promise for multiaddrs event on example

examples/auto-relay/relay.js

@@ -0,0 +1,40 @@
+'use strict'
+
+const Libp2p = require('libp2p')
+const Websockets = require('libp2p-websockets')
+const { NOISE } = require('libp2p-noise')
+const MPLEX = require('libp2p-mplex')
+
+async function main () {
+  const node = await Libp2p.create({
+    modules: {
+      transport: [Websockets],
+      connEncryption: [NOISE],
+      streamMuxer: [MPLEX]
+    },
+    addresses: {
+      listen: ['/ip4/0.0.0.0/tcp/0/ws']
+      // TODO check "What is next?" section
+      // announce: ['/dns4/auto-relay.libp2p.io/tcp/443/wss/p2p/QmWDn2LY8nannvSWJzruUYoLZ4vV83vfCBwd8DipvdgQc3']
+    },
+    config: {
+      relay: {
+        enabled: true,
+        hop: {
+          enabled: true
+        },
+        advertise: {
+          enabled: true,
+        }
+      }
+    }
+  })
+
+  await node.start()
+
+  console.log(`Node started with id ${node.peerId.toB58String()}`)
+  console.log('Listening on:')
+  node.multiaddrs.forEach((ma) => console.log(`${ma.toString()}/p2p/${node.peerId.toB58String()}`))
+}
+
+main()