github/workflows: add prettier cache

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.github/workflows/ci.yml

@@ -102,9 +102,6 @@ jobs:
       - name: type checking and declarations
         run: yarn tsc:full
 
-      - name: prettier
-        run: yarn prettier:check
-
         # We need to generate the API references as well, so that we can verify the doc links
       - name: check api reports and generate API reference
         run: yarn build:api-reports:only --ci --docs
@@ -246,6 +243,9 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-v${{ matrix.node-version }}-backstage-cli-
 
+      - name: prettier
+        run: yarn prettier:check --cache --cache-location .cache/backstage-cli/.prettier-cache
+
       - name: lint changed packages
         run: yarn backstage-cli repo lint --since origin/master --successCache --successCacheDir .cache/backstage-cli