Add run locally part to read me with docker

Author: Geshan Manandhar

readme.md

@@ -15,3 +15,10 @@ This is a demo repo for Laravel 6 on Google Cloud Run. This repo has an example
 
 [![Run on Google Cloud](https://storage.googleapis.com/cloudrun/button.svg)](https://console.cloud.google.com/cloudshell/editor?shellonly=true&cloudshell_image=gcr.io/cloudrun/button&cloudshell_git_repo=https://github.com/geshan/laravel6-on-google-cloud-run.git)
 
+### To run it locally
+
+To run it locally with docker and docker-compose execute the following command:
+
+```bash
+docker-compose up
+```