Enforce usage of selector functions on state in sagas

[damrem]

For the same reasons than https://github.com/pgilad/eslint-plugin-react-redux/blob/master/docs/rules/use-selectors-on-state.md, we should enforce usage of selector functions on state in sagas.

[pke]

Thanks for the suggestion. Will you be able to work on a PR? I can't say when I will be able to work on it.

[pke]

@damrem can you give me an example where this should be enforced with sagas?