No web processes running

My static.json configuration is:

{
  "root": "build/distributions",
  "clean_urls": true,
  "error_page": "build/distributions",
  "routes": {
    "/**": "index.html"
  }
}

run heroku static:deploy output:

$: heroku static:deploy
(node:30480) DeprecationWarning: Archiver.bulk() deprecated since 0.21.0
Uploading app
Creating build

-----> Building on the Heroku-20 stack
-----> Using buildpack: https://github.com/hone/heroku-buildpack-static
-----> Static HTML app detected
-----> Installed nginx 1.19.0 to /app/bin
-----> Discovering process types
       Procfile declares types     -> (none)
       Default types for buildpack -> web

-----> Compressing...
       Done: 7.8M
-----> Launching...
       Released v21
       https://kotlin-js.herokuapp.com/ deployed to Heroku

But I access my app , heroku log output:

021-07-26T06:38:24.688806+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/index" host=kotlin-js.herokuapp.com request_id=4b346279-40d7-4ddb-a358-130d8414ac0f fwd="101.224.155.158" dyno= connect= service= status=503 bytes= protocol=https
2021-07-26T06:38:25.210799+00:00 heroku[router]: at=error code=H14 desc="No web processes running" method=GET path="/favicon.ico" host=kotlin-js.herokuapp.com request_id=642045bf-4fe5-491b-b8fc-2bb990c351c7 fwd="101.224.155.158" dyno= connect= service= status=503 bytes= protocol=https

Why No web processes running ?

heroku / heroku-buildpack-static

No web processes running #219