Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -1,13 +1,15 @@
 image: cirrusci/flutter
 
 stages:
-- coverage
+  - coverage
+  - docs
 
 variables:
   LC_ALL: "en_US.UTF-8"
   LANG: "en_US.UTF-8"
 
 coverage:
+  image: cirrusci/flutter
   stage: coverage
   coverage: '/^\s+lines.+: (\d+.\d*%)/'
   dependencies: []
@@ -16,3 +18,16 @@ coverage:
     - ./scripts/test.sh
     - ./scripts/coverage.sh
     - flutter pub pub publish --dry-run
+
+docs:
+  stage: docs
+  scripts:
+  - image: cirrusci/flutter
+    script:
+    - dartdoc
+  - image: ruby:2.3
+    script:
+    - cd docs/api/ && bundle exec jekyll build -d test
+    - cd docs/api/ && bundle exec jekyll build -d public
+  only:
+  - master