Upload firmware artifact of CI builds

.github/workflows/ci.yaml

@@ -49,6 +49,9 @@ jobs:
         uses: dtolnay/rust-toolchain@stable
         with:
           targets: riscv32imc-unknown-none-elf
+      - name: Install espflash
+        run: cargo install cargo-espflash
+        working-directory: .
       - name: Check out repository
         uses: actions/checkout@v4
       - name: Cache cargo data
@@ -61,3 +64,11 @@ jobs:
           key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
       - name: Build everything
         run: cargo build --workspace --all-targets --release
+      - name: Generate ESP32 image
+        run: cargo espflash save-image --chip esp32c3 --release target/touch-n-drink-esp32c3.bin
+      - name: Upload firmware artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: touch-n-drink
+          path: target/touch-n-drink-*.bin
+          if-no-files-found: error