chore(ci): build images also on pushes on main

.github/workflows/build_image.yml

@@ -1,6 +1,8 @@
-name: Build environment image
+name: Build images
 
 on:
+  push:
+    branches: [main]
   release:
     types: [ published ]
 
@@ -25,14 +27,15 @@ jobs:
 
       - name: Store version number (on release)
         id: version
+        if: ${{ github.event_name == 'release' }}
         # GITHUB_REF looks like "refs/tags/0.3.1" - we need to extract the actual version without the v prefix
         run: echo "number=${GITHUB_REF##*/}" >> $GITHUB_OUTPUT
 
       # Build all images
       - name: Build and push "base" image
         uses: docker/build-push-action@v4
         with:
-          push: true
+          push: ${{ github.event_name == 'release' }}
           context: images/base
           tags: |
             blsq/openhexa-base-environment:${{ steps.version.outputs.number }}
@@ -43,7 +46,7 @@ jobs:
       - name: Build and push "legacy" image
         uses: docker/build-push-action@v4
         with:
-          push: true
+          push: ${{ github.event_name == 'release' }}
           context: images/legacy
           tags: |
             blsq/openhexa-legacy-environment:${{ steps.version.outputs.number }}
@@ -54,11 +57,10 @@ jobs:
       - name: Build and push "blsq" image
         uses: docker/build-push-action@v4
         with:
-          push: true
+          push: ${{ github.event_name == 'release' }}
           context: images/blsq
           tags: |
             blsq/openhexa-blsq-environment:${{ steps.version.outputs.number }}
             blsq/openhexa-blsq-environment:latest
           cache-from: type=gha
-          cache-to: type=gha,mode=max
-
+          cache-to: type=gha,mode=max