As per @gcorne's suggestion, when calling `wp.mce.views.register()`, automatically set `shortcode` equal to the passed `type` in the set of default args instead of introducing a `type` property. It is still overrideable by the args that are passed.

See #28458.



git-svn-id: https://develop.svn.wordpress.org/trunk@28689 602fd350-edb4-49c9-b593-d223f7449a82