Add concurrency rules to workflows (#420)

.github/workflows/ci.yml

@@ -8,6 +8,11 @@ on:
 permissions:
   contents: read
 
+concurrency:
+  # yamllint disable-line rule:line-length
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   ci:
     name: ${{ matrix.name }}

.github/workflows/docker.yml

@@ -13,6 +13,11 @@ permissions:
   contents: read
   packages: write
 
+concurrency:
+  # yamllint disable-line rule:line-length
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build-image:
     runs-on: ubuntu-latest