feat(SidebarTab): allow to postpone component definition

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

Author: susnux

lib/sidebar/SidebarTab.ts

@@ -32,7 +32,7 @@ export interface ISidebarContext {
  * @see https://developer.mozilla.org/en-US/docs/Web/API/Web_components
  * @see https://vuejs.org/guide/extras/web-components#building-custom-elements-with-vue
  */
-export interface SidebarComponent extends HTMLElement, ISidebarContext {
+export interface SidebarTabComponent extends ISidebarContext {
 	/**
 	 * This method is called by the files app if the sidebar tab state changes.
 	 *
@@ -41,6 +41,11 @@ export interface SidebarComponent extends HTMLElement, ISidebarContext {
 	setActive(active: boolean): Promise<void>
 }
 
+/**
+ * The instance type of a sidebar tab web component.
+ */
+export type SidebarTabComponentInstance = SidebarTabComponent & HTMLElement
+
 /**
  * Implementation of a custom sidebar tab within the files app.
  */
@@ -82,6 +87,14 @@ export interface ISidebarTab {
 	 * @param context - The current context of the files app
 	 */
 	enabled: (context: ISidebarContext) => boolean
+
+	/**
+	 * Called when the sidebar tab is registered in the sidebar.
+	 * This can be used to call the `CustomElementRegistry.define()` method to register the web component.
+	 *
+	 * The sidebar itself will anyways wait for the component to be defined in the registry (`customElements.whenDefined()`).
+	 */
+	register?: () => Promise<void>
 }
 
 /**