Update CI settings

Author: jamesmunns

.gitlab-ci.yml

@@ -7,8 +7,12 @@ books:
     - mdbook build
     - cd ../embedonomicon
     - mdbook build
+  after_script:
+    - curl -X POST -F token=$DEPLOY_DOCS_TRIGGER_TOKEN -F ref=master https://gitlab.onevariable.com/api/v4/projects/8/trigger/pipeline
   artifacts:
     paths:
       - books/embedded-rust-book/book
       - books/embedonomicon/book
     expire_in: 1 month
+  only:
+    - master