feat: add caching for Rust dependencies in documentation workflow

Author: eltorio

.github/workflows/docs.yml

@@ -39,7 +39,9 @@ jobs:
         uses: dtolnay/rust-toolchain@v1
         with:
           toolchain: 1.86.0
-            
+      - name: Cache dependencies
+        uses: Swatinem/rust-cache@v2
+
       - name: Build documentation
         run: |
           # Build documentation with all features