fix: add library usage

Author: seveibar

bin/cli.js

@@ -1,7 +1,4 @@
 #!/usr/bin/env node
 
-const micro = require("micro")
-const app = require("../app")
-const service = micro(app)
-console.log("Running UDT collaboration server on port 3000")
-service.listen(3000)
+const run = require("../index")
+run()

index.js

@@ -0,0 +1,8 @@
+const micro = require("micro")
+const app = require("./app")
+
+module.exports = ({ port = 3000 } = {}) => {
+  const service = micro(app)
+  console.log(`Running UDT collaboration server on port ${port}`)
+  service.listen(port)
+}