ci: automatic push to github

- issue solved with https://stackoverflow.com/questions/63451263/sync-two-git-repositories

Refs #11
2 jobs for master in 1 minute and 38 seconds (queued for 14 seconds)
Status Name Job ID Coverage
  Check
passed check #193017
docker

00:01:21

 
  Github
failed github #193018
docker

00:00:16

 
Name Stage Failure
failed
github Github
Identity added: (stdin) (github)
$ mkdir -p ~/.ssh
$ chmod 700 ~/.ssh
$ git config --global user.email "gitlab@inrae.fr"
$ git config --global user.name "Gitlab CI"
$ git remote add github https://github.com/inrae/hubeau.git
fatal: remote github already exists.
Cleaning up file based variables
ERROR: Job failed: exit code 1