Introduce automated deploy to WP.org

Ported from 10up's GitHub Action: https://github.com/10up/actions-wordpress/blob/598b1572d5024340f09d7efc083a65ebff3bcdef/dotorg-plugin-deploy/entrypoint.sh

.gitlab-ci.yml

@@ -49,6 +49,7 @@ PluginSVN:
   stage: deploy
   image: containers.ethitter.com:443/docker/images/php:7.3
   before_script:
+    - apt-get update
     - apt-get install -y rsync
   script: ./bin/deploy.sh
   when: on_success