Buttons don't become disabled (grayed out) while in source mode

It looks to be an issue on plugin.js, in order to disable the embed buttons on source view.

It is missing the modes on the "addButton".
modes: { wysiwyg : 1, source : 0 },

Fixed version:
editor.ui.addButton(button.id, {
label: button.label,
data: button,
allowedContent: 'drupal-entity[!data-entity-type,!data-entity-uuid,!data-entity-embed-display,!data-entity-embed-display-settings,!data-align,!data-caption,!data-embed-button]',
click: function(editor) {
editor.execCommand('editdrupalentity', this.data);
},
icon: button.image,
modes: { wysiwyg : 1, source : 0 },

How can I send a PR to fix this?

Thanks,