Add menu bar integration to export pdf. (#15970)

Internal (ui): Added menu bar integration for export to PDF. Related to #15894, cksource/ckeditor5-commercial#6058.

packages/ckeditor5-theme-lark/theme/ckeditor5-ui/components/menubar/menubarmenulistitembutton.css

@@ -14,6 +14,18 @@
 		min-width: var(--ck-menu-bar-menu-item-min-width);
 	}
 
+	& > .ck-spinner-container,
+	& > .ck-spinner-container .ck-spinner {
+		/* These styles correspond to .ck-icon so that the spinner seamlessly replaces the icon. */
+		--ck-toolbar-spinner-size: 20px;
+	}
+
+	& > .ck-spinner-container {
+		/* These margins are the same as for .ck-icon. */
+		margin-left: calc(-1 * var(--ck-spacing-small));
+		margin-right: var(--ck-spacing-small);
+	}
+
 	/*
 	 * Hovered items automatically get focused. Default focus styles look odd
 	 * while moving across a huge list of items so let's get rid of them

packages/ckeditor5-ui/src/menubar/utils.ts

@@ -395,6 +395,13 @@ export const MenuBarMenuViewPanelPositioningFunctions: Record<string, Positionin
  * It contains names of all UI components available in the project.
  */
 export const DefaultMenuBarConfig: MenuBarConfig = [
+	{
+		id: 'file',
+		label: 'File',
+		items: [
+			'menuBar:exportPdf'
+		]
+	},
 	{
 		id: 'edit',
 		label: 'Edit',