chore: add starter integration test to ci (#2660)

## What's the purpose of this pull request?

For every pull request we do on faststore we must test the package
against the starter. This is time consuming, and non error-prone since
the local setup of each developer can vary.

The test runs on ci, and:

1. build the packages
2. generate a tarball for them with npm pack
3. clone the starter
4. install the packaged packages
5. run build

.github/workflows/ci.yml

@@ -28,7 +28,7 @@ jobs:
           cache: 'yarn'
 
       - name: Install dependencies
-        run: yarn
+        run: yarn --frozen-lockfile
 
       - name: Build
         run: yarn build
@@ -41,3 +41,32 @@ jobs:
 
       - name: Test
         run: yarn test
+
+      - name: Pack packages
+        run: |
+          mkdir -p packed-packages
+          for package in packages/*; do
+            if [ -d "$package" ]; then
+              (cd "$package" && npm pack --pack-destination ../../packed-packages)
+            fi
+          done
+
+      - name: Clone starter
+        run: git clone https://github.com/vtex-sites/starter.store.git starter
+
+      - name: Install the packages on starter
+        run: |
+          cd starter
+          for package in ../packed-packages/*.tgz; do
+            yarn add "$package"
+          done
+
+      - name: Install dependencies in starter
+        run: |
+          cd starter
+          yarn install --frozen-lockfile
+
+      - name: Build starter
+        run: |
+          cd starter
+          yarn build