Add how-to-use instructions in README

1 job for 0.0.1 in 13 seconds (queued for 1 second)
Status Name Job ID Coverage
failed pouet-it #281508


Name Stage Failure
pouet-it Test
Cloning into '/builds/fiat-tux/hat-softwares/mastodon/pouet-it-from-ci'...
Checking out 35a8f017 as 0.0.1...
Skipping Git submodules setup
$ cd /opt/pouet-it-from-ci
$ export MESSAGE="Je viens de sortir une nouvelle version de ${CI_PROJECT_NAME} !\n${CI_PROJECT_URL}/tags/${CI_COMMIT_TAG}"
$ carton exec ./
Global symbol "%END" requires explicit package name (did you forget to declare "my %END"?) at ./ line 23.
Execution of ./ aborted due to compilation errors.
ERROR: Job failed: exit code 1