Change flat config to an array to accept *.vue

[ota-meshi]

This PR changes the flat config to an array to accept *.vue extensions.

I noticed that using the following flat config I receive the following message:

File ignored because of a matching ignore pattern. Use "--no-ignore" to disable file ignore settings or use "--no-warn-ignored" to suppress this warning.

const plugin = require('eslint-plugin-vue')
module.exports = [
  plugin.configs['flat/base'],
  {
    rules: {
      'vue/no-duplicate-attributes': 'error'
    }
  }
]

I think this is because the flat config does not include the *.vue extension in files.

I was thinking of adding files: ['*.vue'] to all configs, but that doesn't work because some of the rules of this plugin can also be used in *.js files. Therefore, we added files: ['*.vue'] only to the config that has a parser and modified it to provide the config as an array.

@aladdin-add I would like to hear your opinion if possible.

[aladdin-add]

I always like to export an object (if possible). the usage can be like:

const plugin = require('eslint-plugin-vue');

module.exports = [
  {files: ["**/*.js", "**/*.vue"], plugin.configs['flat/base']},
];

If you export the array format it will be difficult for the user to combine them, e.g. to add "*.ts".

[ota-meshi]

I think that the only way to properly specify the extension to apply the configuration provided in the array is as follows.

const plugin = require('eslint-plugin-vue');
module.exports = [
  ...plugin.configs['flat/base'].map((config) => ({
    ...config,
    files: ["**/*.js", "**/*.vue"]
  })),
]

I agree that objects are easier to handle, but I don't think it's possible in this case 🤔

[aladdin-add]

the flat config docs should show it's exporting an array, otherwise LGTM!

[ota-meshi]

Thank you for the review! I have fixed the documentation.

[FloEdelmann]

I added some commits with small changes, as that was easier than describing in comments what I am suggesting. Feel free to comment/revert them. Otherwise, this is fine from my side 🙂
Thanks! Let's get flat config support shipped 🚀

[ota-meshi]

Thanks for fixing the documentation!