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/test-all.js

@@ -0,0 +1,33 @@
+'use strict'
+
+process.on('unhandedRejection', (err) => {
+  console.error(err)
+
+  process.exit(1)
+})
+
+const path = require('path')
+const fs = require('fs')
+const {
+  waitForOutput
+} = require('./utils')
+
+async function testAll () {
+  for (const dir of fs.readdirSync(__dirname)) {
+    if (dir === 'node_modules' || dir === 'tests_output') {
+      continue
+    }
+
+    const stats = fs.statSync(path.join(__dirname, dir))
+
+    if (!stats.isDirectory()) {
+      continue
+    }
+
+    await waitForOutput('npm info ok', 'npm', ['test', '--', dir], {
+      cwd: __dirname
+    })
+  }
+}
+
+testAll()