Improve documentation

background.js

@@ -48,7 +48,7 @@ function updateStorageFromCookies() {sites.forEach((site) => {
 /**
  * Get count (max 10) tokens and store them in the stash
  * @param {number} count
- * @returns {boolean} True if successfull, false otherwise.
+ * @returns {Promise<boolean>} Resolves to true if successfull, false otherwise.
  */
 function refillTokenStash(count) { // TODO: handle count >10
   console.log("refilling tokens");