Exclude .storybook from ESLint's default hidden directory ignore list via .eslintignore to allow linting of Storybook configuration files

[Shyam-Raghuwanshi]

Filter out ESLint-ignored files (e.g., files in hidden directories
like .storybook) before passing them to ESLint in the volto package
lint-staged configuration.

This prevents pre-commit hook failures when staging files from hidden
directories, as ESLint ignores these files by default and the
'--max-warnings=0' flag treats the warning as a fatal error.

• I signed and returned the Plone Contributor Agreement, and received and accepted an invitation to join a team in the Plone GitHub organization.
• I verified there aren't other open pull requests for the same change.
• I followed the guidelines in Contributing to Volto.
• I successfully ran code linting checks on my changes locally.
• I successfully ran unit tests on my changes locally.
• I successfully ran acceptance tests on my changes locally.
• If needed, I added new tests for my changes.
• If needed, I added documentation for my changes, either in the Storybook or narrative documentation.
• I included a change log entry in my commits.

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Closes #7894

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[wesleybl]

@Shyam-Raghuwanshi I've thought about it some more and I think the files in .storybook should be analyzed. So I think the best solution here is to explicitly tell ESLint not to ignore the .storybook folder.

[wesleybl]

@Shyam-Raghuwanshi Thanks!

Could you please do a backport to Volto 18?