add docs to UmbLitElement

src/shared/lit-element/lit-element.element.ts

@@ -1,8 +1,31 @@
 import { LitElement, property } from '@umbraco-cms/backoffice/external/lit';
 import { UmbElementMixin } from '@umbraco-cms/backoffice/element-api';
 
+/**
+ * The base class for all Umbraco LitElement elements.
+ *
+ * @abstract
+ * @remarks This class is a wrapper around the LitElement class.
+ * @remarks The `dir` and `lang` properties are defined here as reactive properties so they react to language changes.
+ */
 export class UmbLitElement extends UmbElementMixin(LitElement) {
-	// Make `dir` and `lang` reactive properties so they react to language changes:
-	@property() dir = '';
+	/**
+	 * The direction of the element.
+	 *
+	 * @attr
+	 * @remarks This is the direction of the element, not the direction of the backoffice.
+	 * @example 'ltr'
+	 * @example 'rtl'
+	 */
+	@property() dir: 'rtl' | 'ltr' | '' = '';
+
+	/**
+	 * The language of the element.
+	 *
+	 * @attr
+	 * @remarks This is the language of the element, not the language of the backoffice.
+	 * @example 'en-us'
+	 * @example 'en'
+	 */
 	@property() lang = '';
 }