Add an option to allow packages to be transpiled

[titouanmathis]

With the current configuration in v2.9.0, if we need to add packages installed with NPM to the Babel transpilation, we need to override the Webpack config as follows:

module.exports = {
  webpack(config) {
    const [babel] = config.module.rules;
    babel.exclude = [
      /node_modules/,
      { not: [/@namespace\/package/, /other-package/] },
    ];
  },
};

It could be useful to have an option to easily manage this kind of modification, i.e.:

module.exports = {
  transpileInclude: ['@namespace/package', /other-package-(one|twog)/],
};

[titouanmathis]

Partially fixed in v3.1.0-alpha.1 for packages in the @studiometa/* namespace.