Add workflows on stable

.github/workflows/docker.yml

@@ -2,7 +2,7 @@ name: Build
 
 on:
   push:
-    branches: [ master ]
+    branches: [ master, stable ]
 
   workflow_dispatch:
 
@@ -12,6 +12,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
+
       -
         name: Set up QEMU
         uses: docker/setup-qemu-action@v1
@@ -34,7 +35,7 @@ jobs:
         uses: docker/build-push-action@v2
         with:
           push: true
-          tags: plausible/analytics:master
+          tags: plausible/analytics:${GITHUB_REF##*/}
           cache-from: type=local,src=/tmp/.buildx-cache
           cache-to: type=local,dest=/tmp/.buildx-cache
       -

.github/workflows/elixir.yml

@@ -2,9 +2,9 @@ name: Elixir CI
 
 on:
   push:
-    branches: [ master ]
+    branches: [ master, stable ]
   pull_request:
-    branches: [ master ]
+    branches: [ master, stable ]
 
 jobs:
   build: