Please add a .info.yml file so coder can work with packages.drupal.org

Coder, being "special" and not a module doesnt currently work with packages.drupal.org, because we're only able to store exisiting composer.json data alongside a "component", which happens to be a module or theme, and is defined by having an .info.yml file.

So, in order to make coder have the proper composer dependencies and package type that comes from its composer.json, we need to trick the drupal.org infrastructure into thinking its a module by adding an info.yml file.

The only downside is that it may cause coder to show up in the list of installable/enableable modules.

But the upside is that we can transition core and other contrib composer requirements away from the 8.1.12 style version numbers and reliance on packagist.org and the github.com/klausi/coder mirror, and have it follow a more typical pattern that other drupal things are doing now.