Add Cargo caching for faster builds

.forgejo/workflows/botserver.yaml

@@ -16,6 +16,17 @@ jobs:
 
       - uses: actions/checkout@v4
 
+      - name: Cache Cargo registry
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-botserver-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-botserver-
+
       - name: Install Rust
         uses: msrd0/rust-toolchain@v1
         with: