gutenberg 8.x-1.0

Main changes from RC-1:
- Now it's using Gutenberg core files directly. Removed Gutenberg-JS dependency. Based on Gutenberg version 5.6.1.
- Better media files handling - support to store title, caption and alternative text.
- New Allowed Blocks UI at content type admin UI.
- And, of course, several bug fixes.

Important information when upgrading from RC-1

When updating Drupal Gutenberg from RC-1 to 1.0 there is some extra steps you need to do so everything keeps working as expected.
- Run update database.
- Go to the content types you have enabled Gutenberg and save them again, even without changing anything. This will store the Allowed blocks settings on the database, otherwise blocks won’t show when trying to insert them on a node.
- Mind that it’s a quite impactful upgrade regarding the Gutenberg library (from 4.8.0 to 5.6.1) so, if any block becomes invalid, try to Attempt Block Recovery option available at the block options context menu.