Improve CI

Add more tests to the CI, including a docker build test, and add the
generation and publication of a new docker image on master and tags

.drone.yml

@@ -1,6 +1,7 @@
+# Test building the code and docker image
 kind: pipeline
 type: docker
-name: Tests
+name: test-build
 
 steps:
 - name: go-test
@@ -31,6 +32,11 @@ steps:
   privileged: true
   settings:
     repo: git.faercol.me/faercol/public-ip-tracker
+    registry: git.faercol.me
+    tags: latest
+    username: faercol
+    password:
+      from_secret: GIT_PASSWORD
   depends_on:
     - go-test
     - go-build
@@ -39,4 +45,24 @@ steps:
 trigger:
   event:
     - push
+
+# On a tag, only build the related docker image
+kind: pipeline
+type: docker
+name: Release
+
+steps:
+- name: docker-push-tag
+    image: thegeeklab/drone-docker-buildx
+  privileged: true
+  settings:
+    registry: git.faercol.me
+    repo: git.faercol.me/faercol/public-ip-tracker
+    auto_tag: true
+    username: faercol
+    password:
+      from_secret: GIT_PASSWORD
+
+trigger:
+  event:
     - tag