chore(ci): add m2 cache

.github/workflows/build-desktop-release.yml

@@ -37,6 +37,12 @@ jobs:
         with:
           java-version: 1.8
 
+      - name: Cache local Maven repository
+        uses: actions/cache@v2
+        with:
+          path: ~/.m2/repository
+          key: ${{ runner.os }}-maven
+
       - name: Install clojure
         run: |
           curl -O https://download.clojure.org/install/linux-install-1.10.1.763.sh