chore(ckeditor5-keyboard-marker): port source code

packages/ckeditor5-keyboard-marker/src/kbdediting.ts

@@ -0,0 +1,38 @@
+import { AttributeCommand, Plugin } from "ckeditor5";
+
+const KBD = 'kbd';
+
+/**
+ * The keyboard shortcut (`kbd`) editing feature.
+ *
+ * It registers the `'kbd'` command, associated keystroke and introduces the
+ * `kbd` attribute in the model which renders to the view as a `<kbd>` element.
+ */
+export default class KbdEditing extends Plugin {
+
+	public static get pluginName() {
+		return 'KbdEditing' as const;
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	init() {
+		const editor = this.editor;
+
+		// Allow kbd attribute on text nodes.
+		editor.model.schema.extend( '$text', { allowAttributes: KBD } );
+		editor.model.schema.setAttributeProperties( KBD, {
+			isFormatting: true,
+			copyOnEnter: true
+		} );
+
+		editor.conversion.attributeToElement( {
+			model: KBD,
+			view: KBD
+		} );
+
+		editor.commands.add( KBD, new AttributeCommand( editor, KBD ) );
+		editor.keystrokes.set( 'CTRL+ALT+K', KBD );
+	}
+}