fix: add storybook demos to eslint config

[jzempel]

Description

This PR adds missing demo directories 😬 to eslint.

Detail

A less disruptive version of #1956. I learned that strategies could be selectively applied for eslint --fix autofixing – resulting in a lower impact PR. Material changes are:

• 9f6a4d8 (updated config)
• c92ac40 (address remaining lint errors)

[coveralls]

coverage: 95.896%. remained the same
when pulling c92ac40 on jzempel/demo-lint
into bbe1263 on main.

[ze-flo]

I like this better! 💯