FEATURE: Add ARM processor variant to custom PHP docker image (#505)

* Testing pushing for arm64 image build.

* Reverting branch back to master now that we know it works.

---------

Co-authored-by: Arvin Singla <arvinsingla@Arvins-MacBook-Air.local>

.github/workflows/build-docker-dev-image.yaml

@@ -6,6 +6,7 @@ on:
       - 'master'
     paths:
       - 'docker/php/Dockerfile'
+      - '.github/workflows/build-docker-dev-image.yaml'
 
 jobs:
   deploy-dev-image:
@@ -26,5 +27,6 @@ jobs:
         uses: docker/build-push-action@v5
         with:
           context: ./docker/php
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: formulize/php-dev:latest