Check all crates in workspace for outdated deps

Author: dtolnay

.github/workflows/ci.yml

@@ -40,4 +40,4 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - uses: dtolnay/install@cargo-outdated
-      - run: cargo outdated --exit-code 1
+      - run: cargo outdated --workspace --exit-code 1