create "stable" tag for Docker Hub images

The stable image should automatically update when we make a new release (along with a new image with the version number). If users wish to use an older version, they will need to update the .env file with that version tag.

Already manually pushed v1.29 to stable tag image.

.env

@@ -1,6 +1,6 @@
 # 4CAT Version: Update with latest release tag or 'latest'
 # https://hub.docker.com/repository/docker/digitalmethodsinitiative/4cat/tags?page=1&ordering=last_updated
-DOCKER_TAG=v1.29
+DOCKER_TAG=stable
 
 # Database setup
 POSTGRES_USER=fourcat

.github/workflows/docker_new_release.yml

@@ -14,19 +14,19 @@ jobs:
     steps:
       - name: Check out the repo
         uses: actions/checkout@v3
-      
+
       - name: Log in to Docker Hub
         uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
         with:
           username: ${{ secrets.DOCKER_DALE_LOGIN }}
           password: ${{ secrets.DOCKER_DALE_PASSWORD }}
-      
+
       - name: Extract metadata (tags, labels) for Docker
         id: meta
         uses: docker/metadata-action@98669ae865ea3cffbcbaa878cf57c20bbf1c6c38
         with:
           images: digitalmethodsinitiative/4cat
-      
+
       - name: Build and push Docker image
         uses: docker/build-push-action@ad44023a93711e3deb337508980b4b5e9bcdc5dc
         with:
@@ -35,3 +35,12 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+
+      # Update the stable tag image
+      - name: Build and push "stable" Docker image
+        uses: docker/build-push-action@ad44023a93711e3deb337508980b4b5e9bcdc5dc
+        with:
+          context: .
+          file: docker/Dockerfile
+          push: true
+          tags: digitalmethodsinitiative/4cat:stable