Enable Drone integration

.drone.yml

@@ -0,0 +1,11 @@
+kind: pipeline
+name: default
+trigger:
+  branch:
+    - free
+steps:
+  - name: build
+    image: maven:3-eclipse-temurin-17
+    commands:
+      - mvn install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
+      - mvn test -B