docs: eslint-plugin-dev readme add eslint 8+ unsupported

[MikeMcC399]

• closes @cypress/eslint-plugin-dev not compatible with ESLint v8 and later #29344

Additional details

Attempting to lint @cypress/eslint-plugin-dev with ESLint v8 fails with:

Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Failed to load plugin '@cypress/dev' declared in '.eslintrc.json': Package subpath './lib/rules/arrow-body-style' is not defined by "exports"

The ESLint Migrate to v8.0.0 document describes the following in the section The /lib entrypoint has been removed:

Beginning in v8.0.0, ESLint is strictly defining its public API. Previously, you could reach into individual files such as require("eslint/lib/rules/semi") and this is no longer allowed. There are a limited number of existing APIs that are now available through the /use-at-your-own-risk entrypoint for backwards compatibility, but these APIs are not formally supported and may break or disappear at any point in time.

The following code shows that @cypress/eslint-plugin-dev is using require in the way that is described as no longer allowed in ESLint 8.x.

cypress/npm/eslint-plugin-dev/lib/custom-rules/arrow-body-multiline-braces.js

Line 2 in 768afcc

const arrowBodyStyle = require('eslint/lib/rules/arrow-body-style')

Steps to test

1. https://github.com/cypress-io/eslint-plugin-cypress is configured with eslint@^7.32.0 and with @cypress/eslint-plugin-dev@3.9.1. The CircleCI workflow confirms that linting is successful with ESLint 7.x.
2. The steps to reproduce in @cypress/eslint-plugin-dev not compatible with ESLint v8 and later #29344 show that @cypress/eslint-plugin-dev@5.3.3 (latest available version) fails with ESLint 8.x.

How has the user experience changed?

There is no change to the end-user experience. This is a documentation-only change which affects Cypress developers only.

PR Tasks

• [na] Have tests been added/updated?
• [na] Has a PR for user-facing changes been opened in cypress-documentation?
• [na] Have API changes been updated in the type definitions?

[cypress-app-bot]

• Create a Draft Pull Request if your PR is not ready for review. Mark the PR as Ready for Review when you're ready for a Cypress team member to review the PR.

[jennifer-shehane]

@MikeMcC399 Thanks for the clarity on this.