add legacy node for cspell

.gitea/workflows/ci.yaml

@@ -14,6 +14,10 @@ jobs:
       - uses: oven-sh/setup-bun@v2
         with:
           bun-version-file: ".bun-version"
+      # only required for cspell compatibility until a mature replacement is available
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
       - run: bun install --frozen-lockfile
       - name: Run lint
         run: bun run check:code