[frontend] add linting

[eh-am]

Would be nice to have linting rules for the frontend. We could reuse most of the ones from @grafana/eslint-config:

 {
  "extends": ["@grafana/eslint-config"]
}

Additional ones that would be useful:

• Forcing all imports to be absolute (using alias), this is so that they can be easily overridden downstream.
• Force React to have been imported (i think @grafana/eslint-config already has that, but worth mentioning)

[hi-rustin]

Thanks for writing this out! I am working on this.