feat: upgrade Drone CI to version 2 (#18)

Co-authored-by: Davide Polonio <poloniodavide@gmail.com>
Reviewed-on: #18
Co-authored-by: polpetta <polpetta@poldebra.me>
Co-committed-by: polpetta <polpetta@poldebra.me>

ci/docker-compose.yaml

@@ -3,8 +3,8 @@ version: '3.7'
 
 services:
   server:
-    image: drone/drone:1
-    restart: always
+    image: drone/drone:2
+    restart: unless-stopped
     env_file:
       - env-droneci-server
     networks:
@@ -17,7 +17,7 @@ services:
 
   runner:
     image: drone/drone-runner-docker:1
-    restart: always
+    restart: unless-stopped
     env_file:
       - env-droneci-runner
     networks: