add woodpecker ci

.woodpecker/test.yaml

@@ -0,0 +1,14 @@
+when:
+  - event: push
+    branch:
+      - master
+      - main
+  - event: pull_request
+
+steps:
+  - name: test
+    image: v1.8.1-erlang-alpine
+    commands:
+      - gleam deps download
+      - gleam test
+      - gleam format --check src test