Fix compressed size workflow for pnpm

- Add Node.js setup step (required for pnpm)
- Add pnpm install step to install dependencies before build
- Update checkout action from v2 to v4
- Ensure dependencies are available before running deploy script

Author: captbaritone

.github/workflows/code-size.yml

@@ -7,11 +7,18 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Install pnpm
         uses: pnpm/action-setup@v2
         with:
           version: 9.12.0
+      - name: Use Node.js 20.x
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20.x
+          cache: "pnpm"
+      - name: Install Dependencies
+        run: pnpm install --frozen-lockfile
       - uses: preactjs/compressed-size-action@v2
         with:
           repo-token: "${{ secrets.GITHUB_TOKEN }}"