Support of EsLint with CRA4

[alexasselin008]

As noted in this issue, eslint-loader has been deleted from create-react-app in version 4.0. Now eslint is being delivered through eslint-webpack-plugin, not eslint-loader. ­reference.

This PR adds the following code :

• 3 new method (getPlugin, removePlugins, pluginByName) in a new file plugin.js
• modification in eslint.js to support eslint being loaded from a plugin instead of a loader.
• After discussing with Craco Author @patricklafrance, this project will no longer be backward compatible. It will only support the latest version of CRA.

[alexasselin008]

Release Notes

Migration Path from 5.8.0

Eslint-loader has been deleted from create-react-app in version 4.0. Now eslint is being delivered through eslint-webpack-plugin, not eslint-loader.
View Changes.

The property loaderOptions is now named pluginOptions

CRACO 5.8

    eslint: {
        enable: true /* (default value) */,
        mode: "extends" /* (default value) */ || "file",
        configure: { /* Any eslint configuration options: https://eslint.org/docs/user-guide/configuring */ },
        configure: (eslintConfig, { env, paths }) => { return eslintConfig; },
        --> loaderOptions: { /* Any eslint-loader configuration options: https://github.com/webpack-contrib/eslint-loader. */ },
        --> loaderOptions: (eslintOptions, { env, paths }) => { return eslintOptions; }
    },

CRACO 6.0

    eslint: {
        enable: true /* (default value) */,
        mode: "extends" /* (default value) */ || "file",
        configure: { /* Any eslint configuration options: https://eslint.org/docs/user-guide/configuring */ },
        configure: (eslintConfig, { env, paths }) => { return eslintConfig; },
        --> pluginOptions: { /* Any eslint-loader configuration options: https://eslint.org/docs/developer-guide/nodejs-api#%E2%97%86-new-eslint-options. */ },
        --> pluginOptions: (eslintOptions, { env, paths }) => { return eslintOptions; }
    },

[patricklafrance]

🥇 thanks for taking care of this @alexasselin008