ci: Update to newer yarn, plus run CI on Node 20 too

.github/workflows/node.js.yml

@@ -5,26 +5,26 @@ name: Node.js CI
 
 on:
   push:
-    branches: [ "main" ]
+    branches: ['main']
   pull_request:
-    branches: [ "main" ]
+    branches: ['main']
 
 jobs:
   build:
-
     runs-on: ubuntu-latest
 
     strategy:
       matrix:
-        node-version: [18.x]
+        node-version: [18.x, 20.x]
         # See supported Node.js release schedule at https://nodejs.org/en/about/releases/
 
     steps:
-    - uses: actions/checkout@v3
-    - name: Use Node.js ${{ matrix.node-version }}
-      uses: actions/setup-node@v3
-      with:
-        node-version: ${{ matrix.node-version }}
-        cache: 'yarn'
-    - run: yarn install --frozen-lockfile
-    - run: yarn ci
+      - uses: actions/checkout@v3
+      - run: corepack enable
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v3
+        with:
+          node-version: ${{ matrix.node-version }}
+          cache: 'yarn'
+      - run: yarn install --immutable
+      - run: yarn ci