Adds an example for Gitlab CI

[kiklop74]

Fixes #39

[Menrath]

@kiklop74 I also use a GitLab CI based on this PR with the newest version of the plugin-ci I get WARNING: Problem calling HTML validator - please report bug to integration team. on the Mustache linting tests. Can you reproduce that?

[kiklop74]

@kiklop74 I also use a GitLab CI based on this PR with the newest version of the plugin-ci I get WARNING: Problem calling HTML validator - please report bug to integration team. on the Mustache linting tests. Can you reproduce that?

Without knowing the actual underlying error, it would be hard to offer solution. Mustache validator depends on Java which I do install using apt-get -yqq install default-jre-headless in the example. I am willing to look into specifics on your side. Contact me and we can work something out. @Menrath

[PhMemmel]

I'm also running moodle-plugin-ci with gitlab pipeline. Mustache linting works for me when using apt install default-jre. Still possible that your issue is different, but as far as I can remember that solved it for me.