ci: automatic push to github

- issue existing remote github (don't know how it is persistent between 2 pipelines)

Refs #11

.gitlab-ci.yml

@@ -66,5 +66,5 @@ github:
     - git config --global user.email "gitlab@inrae.fr"
     - git config --global user.name "Gitlab CI"
   script:
-    - git remote add github https://github.com/inrae/hubeau.git
+    - git remote add github https://github.com/inrae/hubeau.git || exit 0
     - git push --mirror github