Render alert on contributing guide mentioning CODEOWNERS

[jviotti]

Add an alert at the bottom of the contributing doc saying something like: "if you need any help, please ping @, @, or @", where the users are the handles on CODEOWNERS, which we already parse in meta.json.

[dimitrisnl]

We don't parse codeowners just yet, can you please remind me how to update meta.json?

[jviotti]

@dimitrisnl You can update https://github.com/balena-io/landr/blob/master/scripts/scrutinizer-stub.js and then run node scripts/scrutinizer-stub.js > meta.json

[jviotti]

@dimitrisnl Looks like we already do this: https://github.com/balena-io/landr/blob/master/scripts/scrutinizer-stub.js#L155

[dimitrisnl]

Ah great, it was under maintainers