Offer to maintain Migrate Default Content

I asked the people that I'm aware that used the module and they don't actively use it anymore or are migrating to default_content.

I still think is a good technical idea to rely on migrate for importing and rolling back content but in the day-to-day of our projects for clients using default_content is easier because all of the features it includes.

If I were to contribute to this project now I would make it a priority to have a format of the YML files that is compatible with the default_content module.

From now I consider you the maintainers of the module and I will open MRs if I want to modify anything. Feel free to commit directly to it.

Happy coding!