Adds @grafana/eslint-plugin-plugins to all examples

[hugohaggmark]

This PR adds @grafana/eslint-plugin-plugins package and changes ESLint config in order to get results for @grafana/eslint-plugin-plugins

Moved the ESLint warnings/errors here: https://github.com/orgs/grafana/projects/76/views/4?sliceBy%5Bvalue%5D=hugohaggmark&pane=issue&itemId=97184296&issue=grafana%7Cgrafana-community-team%7C338

Partially fixes #337

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[leventebalogh]

Nice 🚀

[hugohaggmark]

So I also fixed a bunch of ESLint warnings and an ESLint error in this PR, please have a look @leventebalogh and see if this looks ok, thank you 🙏

[hugohaggmark]

I added you as well to this @jackw 👍

[leventebalogh]

Looks good to me, nice work @hugohaggmark! 👏