Enhancement: Add more platforms (#71)

Author: OskarStark

.github/workflows/build-docker.yaml

@@ -10,6 +10,7 @@ on:
 
 env:
     IMAGE: "oskarstark/phpstan-ga"
+    PLATFORMS: linux/arm/v7,linux/arm64/v8,linux/amd64
 
 jobs:
     build:
@@ -21,6 +22,10 @@ jobs:
               with:
                 ref: '${{ github.head_ref }}'
 
+            - name: 'Exposing Release Version'
+              run: |
+                  echo "RELEASE_VERSION=${GITHUB_REF#refs/*/}" >> $GITHUB_ENV                
+
             - name: Login to Dockerhub
               uses: docker/login-action@v2
               with:
@@ -42,3 +47,4 @@ jobs:
                   context: .
                   cache-from: type=gha
                   cache-to: type=gha,mode=max
+                  platforms: ${{ env.PLATFORMS }}