Require image for ARM64 architecture

Hi Team,

I am trying to use the **amazon/amazon-ecs-sample** image on arm64 platform but it seems it is not available for arm64.

I have successfully built the image using the command **docker build -t image_name .** on the arm64 platform without any changes in the Dockerfile.

I have used **Travis-CI** to build and push the image for both the platforms.

**Commit Link -** https://github.com/odidev/ecs-demo-php-simple-app/commit/b4efb5c716774d4895b08a64ce2f48e396f2e5c1

**Travis link -** https://travis-ci.com/github/odidev/ecs-demo-php-simple-app/builds/221144015

**Docker Hub Link -** https://hub.docker.com/r/odidev/amazon-ecs-sample/tags?page=1&ordering=last_updated

Do you have any plans on releasing arm64 images?

If interested, I will raise a PR.