packages,plugins: add package documentation

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

plugins/user-settings/api-report.md

@@ -119,6 +119,4 @@ export const useUserProfile: () => {
   profile: ProfileInfo;
   displayName: string;
 };
-
-// (No @packageDocumentation comment for this package)
 ```

plugins/user-settings/src/index.ts

@@ -14,6 +14,12 @@
  * limitations under the License.
  */
 
+/**
+ * A Backstage plugin that provides a settings page
+ *
+ * @packageDocumentation
+ */
+
 export {
   userSettingsPlugin,
   userSettingsPlugin as plugin,