Fix JSDoc return type annotations of async functions

These don't return the mentioned type directly, but a promise containing
this type, which has to be await'ed first. This was confusing my IDE's
tslint which suggested await would not be necessary.

src/api.js

@@ -23,7 +23,7 @@ const fetchApi = (path, params = {}) => {
 /**
  * Get the recorder's version.
  *
- * @returns {String} Version
+ * @returns {Promise<String>} Version
  */
 export const getVersion = async () => {
   const response = await fetchApi("/api/0/version");
@@ -36,7 +36,7 @@ export const getVersion = async () => {
 /**
  * Get all users.
  *
- * @returns {User[]} Array of usernames
+ * @returns {Promise<User[]>} Array of usernames
  */
 export const getUsers = async () => {
   const response = await fetchApi("/api/0/list");
@@ -50,7 +50,7 @@ export const getUsers = async () => {
  * Get all devices for the provided users.
  *
  * @param {User[]} users Array of usernames
- * @returns {{User: Device[]}}
+ * @returns {Promise<{User: Device[]}>}
  *   Object mapping each username to an array of device names
  */
 export const getDevices = async (users) => {
@@ -80,7 +80,7 @@ export const getDevices = async (users) => {
  *
  * @param {User} [user] Get last locations of all devices from this user
  * @param {Device} [device] Get last location of specific device
- * @returns {OTLocation[]} Array of last location objects
+ * @returns {Promise<OTLocation[]>} Array of last location objects
  */
 export const getLastLocations = async (user, device) => {
   const params = {};
@@ -107,7 +107,7 @@ export const getLastLocations = async (user, device) => {
  * @param {Device} device Device name
  * @param {String} start Start date and time in UTC
  * @param {String} end End date and time in UTC
- * @returns {OTLocation[]} Array of location history objects
+ * @returns {Promise<OTLocation[]>} Array of location history objects
  */
 export const getUserDeviceLocationHistory = async (
   user,
@@ -141,7 +141,7 @@ export const getUserDeviceLocationHistory = async (
  *   Devices of which the history should be fetched
  * @param {String} start Start date and time in UTC
  * @param {String} end End date and time in UTC
- * @returns {LocationHistory} Location history
+ * @returns {Promise<LocationHistory>} Location history
  */
 export const getLocationHistory = async (devices, start, end) => {
   const locationHistory = {};