Set up basic CI

.drone.yml

@@ -2,17 +2,9 @@ kind: pipeline
 type: docker
 name: default
 
-services:
-  - name: postgres
-    image: docker.io/library/postgres:17.2
-
 steps:
   - name: lint & test
-    image: docker.io/library/elixir:1.18.3-otp-27
+    image: docker.io/elixir:1.18.3-otp-27
     commands:
-      # Install hex package manager
-      - mix local.hex --force
-      # Check for compilation errors & warnings
       - mix compile --warnings-as-errors
-      # Check formatting
       - mix format --check-formatted