Add CSV data_parser

Hi, How to proceed to get this Drupal 10 compliant reade in this module please?
greetings,

I'm not a fan of using league/csv here without it being an actual module dependency, There's no way for someone to know that they must manually add league/csv to use the csv parser. And I don't want to add league/csv as a dependency to migrate plus as most people have no need for it as mentioned in #3

I think what we should do is add the migrate_plus parser plugin to migrate_source_csv alongside the standalone source. That way the league dependency is contained to the module that needs it, and with migrate_source_csv you have the option of the standalone source, or the flexibility of the migrate_plus fetchers if you need them.

@heddn, Thoughts on moving the issue to migrate_source_csv?

Seems like a great suggestion. Moving.

After 6.0.1 → release of migrate plus module, if http data fetcher is in use, an error will occur in \Drupal\migrate_plus\Plugin\migrate_plus\data_parser\Csv::getSourceData() after $response = $this->getDataFetcherPlugin()->getResponseContent($url); returns object instead of a string. This new patch should fix it.

I'm pretty sure this needs a rebase.