add drone ci

.drone.yml

@@ -0,0 +1,28 @@
+kind: pipeline
+type: docker
+name: cannery
+
+cache:
+  mount:
+    - _build
+    - deps
+
+steps:
+- name: test
+  image: bitwalker/alpine-elixir-phoenix:1.13
+  environment:
+    TEST_DATABASE_URL: ecto://postgres:postgres@database/cannery_test
+  commands:
+  - mix local.rebar --force
+  - mix local.hex --force
+  - mix deps.get
+  - npm install --prefix assets
+  - mix test
+
+services:
+- name: database
+  image: postgres:13
+  environment:
+    POSTGRES_USER: postgres
+    POSTGRES_PASSWORD: postgres
+    POSTGRES_DB: postgres