Copy and adapt better CI from Soketto instead. Hopefully cache bits will improve build speed

.github/workflows/frontend.yml

@@ -6,13 +6,16 @@ name: Frontend CI
 on:
   push:
     paths:
-      - '.github/workflows/**'
+      - '.github/workflows/frontend.yml'
       - 'frontend/**'
       - '!backend/**'
 
+defaults:
+  run:
+    working-directory: ./frontend
+
 jobs:
   build:
-
     runs-on: ubuntu-latest
 
     strategy:
@@ -21,27 +24,30 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
+
     - name: Use Node.js ${{ matrix.node-version }}
       uses: actions/setup-node@v1
       with:
         node-version: ${{ matrix.node-version }}
+
     - name: install
-      working-directory: ./frontend
       run: yarn install
+
     - name: check
       run: yarn pretty:check
-      working-directory: ./frontend
+
     - name: Test
       run: yarn test
-      working-directory: ./frontend
+
     - name: Build
-      working-directory: ./frontend
       run: yarn build
+
     - name: Login to Dockerhub
       uses: docker/login-action@v1
       with:
         username: ${{ secrets.DOCKER_USERNAME }}
         password: ${{ secrets.DOCKER_PASSWORD }}
+
     - name: Build and Push template image
       uses: docker/build-push-action@v2 # https://github.com/docker/build-push-action
       if: matrix.node-version == '12.x'