Add dockerfile and build job

.woodpecker/Dockerfile

@@ -0,0 +1,5 @@
+FROM alpine:3.14
+
+RUN apk update
+RUN apk install rustup postgresql
+RUN rustup install stable

.woodpecker/test-workflow.yml

@@ -8,3 +8,18 @@ steps:
     commands:
       - echo "Hello world"
 
+  - name: docker-build
+    image: woodpeckerci/plugin-docker-buildx
+    settings:
+      dockerfile: .woodpecker/Dockerfile 
+      registry: gitea.firechicken.net
+      repo: fedichat
+      username: ${{ gitea.actor }}
+      password: ${{ gitea.token }}
+    when: 
+      - event: push
+        branch: master
+      - event: pull_request
+
+
+