Scripts: Try using cosmiconf for locating tool configs

[ockham]

A number of our scripts in the @wordpress/scripts contain logic to find the relevant config and/or ignore file (or package.json entry) for a given tool by replicating that tool's logic in doing so. E.g. lint-js tries to locate the relevant config for eslint here:

gutenberg/packages/scripts/scripts/lint-js.js

Lines 23 to 33 in dd4cc1b

	// See: https://eslint.org/docs/user-guide/configuring#using-configuration-files-1.
	const hasLintConfig =
	hasArgInCLI( '-c' ) ||
	hasArgInCLI( '--config' ) ||
	hasProjectFile( '.eslintrc.js' ) ||
	hasProjectFile( '.eslintrc.json' ) ||
	hasProjectFile( '.eslintrc.yaml' ) ||
	hasProjectFile( '.eslintrc.yml' ) ||
	hasProjectFile( 'eslintrc.config.js' ) ||
	hasProjectFile( '.eslintrc' ) ||
	hasPackageProp( 'eslintConfig' );

Similar strategies can be found across our other scripts. This has lead to creation of helper methods such as hasProjectFile or hasPackageProp.

Rather than replicating and hard-wiring those tools' strategies, we might consider using a tool like cosmiconf, which seeks to establish somewhat of a standard for config file retrieval across tools. (Here's a broader discussion in the nodejs/tooling repo that had a similar goal but didn't really go anywhere.) AFAIK, some of the tools we use actually use cosmiconf themselves (e.g. prettier), while it has been proposed (but not yet adopted) by others (e.g. eslint).

We could consider multiple strategies:

• Audit our tools, and only switch those to cosmiconf that use it themselves.
• Use it for all our tools, as we might consider it "good enough".

---

Inspired by #30240 (comment)

[gziolo]

We might have an issue with the same proposal already. It was surely discussed in the past but no actions were taken. If you look at the list of possible files used with different tools you will see that there isn't one standard enforced. Anyway, it'd be nice to have cosmiconf integrated 👍🏻