Make sure your SQLite database is at database/database.sqlite and remove the database/.gitignore file.

1. Add "ext-pdo_sqlite": "*" to the require block in composer.json. You can read about how to enable various PHP extensions on Heroku here.
2. Run composer update.
3. Create a Heroku account.
4. Create a new app in the Heroku dashboard and link your GitHub repo to it.
5. Click the "Enable Automatic Deploys" button. Now, every time you push to your GitHub repo, Heroku will automatically deploy your app.
6. Create a file in your repo called Procfile, with the following line: web: vendor/bin/heroku-php-apache2 public/. Push it up to your repo. This will trigger Heroku to deploy your app.
7. Navigate to the Settings tab, and add the following environment variables:

APP_ENV=development
APP_KEY=whatever your key is here ...
APP_DEBUG=true
APP_LOG_LEVEL=debug
DB_CONNECTION=sqlite

You're all set! Click on the "Open app" button and test all of your routes!