Add more linting!

What does this MR do?

I switched from using standard command to using eslint command, but we still base it on the standard eslint preset, so the style is basically the same.

Also added linting for vuejs files, I put it on quite a strict mode (vue/recommended - see https://github.com/vuejs/eslint-plugin-vue#gear-configs).

yarn fix can fix quite a lot of things, so don't think you have to do it all manually.

How confident are you it won't break things if deployed?

Only linting changes, so everything should be ok :)

Links to related issues

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))