chore(lint): Fix linting in fxa-settings package

[pdehaan]

Because

• linting currently fails hard due to missing "lint:sass" script.

This pull request

• removes reference to undefined "lint:sass" script
• moves the ESLint config from the package.json into the more standard/consistent .eslintrc.json file
• lints the hidden .storybook/ folder

Issue that this pull request solves

Closes: #12933

Checklist

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• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).

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[LZoog]

Asked in Slack, but just in case someone else sees this and thinks to merge it, I've asked Peter to fix up his commit to match our guidelines 😎