Generate schema for extension pack metadata

After the upgrade to the correct types for js-yaml, the return type
of `load` is correctly typed as `unknown`. This means that we can't
use the return value directly, but need to validate it first.

This adds such validation by generating a JSON schema for a newly
created typed. The JSON schema generation is very similar to how we do
it in https://github.com/github/codeql-variant-analysis-action.

.github/workflows/main.yml

@@ -99,6 +99,42 @@ jobs:
         run: |
           npm run find-deadcode
 
+  generated:
+    name: Check generated code
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+
+      - uses: actions/setup-node@v3
+        with:
+          node-version: '16.17.1'
+          cache: 'npm'
+          cache-dependency-path: extensions/ql-vscode/package-lock.json
+
+      - name: Install dependencies
+        working-directory: extensions/ql-vscode
+        run: |
+          npm ci
+        shell: bash
+
+      - name: Check that repo is clean
+        run: |
+          git diff --exit-code
+          git diff --exit-code --cached
+
+      - name: Generate code
+        working-directory: extensions/ql-vscode
+        run: |
+          npm run generate
+
+      - name: Check for changes
+        run: |
+          git diff --exit-code
+          git diff --exit-code --cached
+
   unit-test:
     name: Unit Test
     runs-on: ${{ matrix.os }}