add docstrings

Author: DenisaCG

src/token.ts

@@ -1,9 +1,15 @@
 import { Token } from '@lumino/coreutils';
 
+/**
+ * A token for the plugin that provides the list of drives.
+ */
 export const IDrivesList = new Token<IDriveInfo[]>(
   '@jupyter/drives:drives-list-provider'
 );
 
+/**
+ * An interface for the available drives.
+ */
 export interface IDriveInfo {
   name: string;
   region: string;