add: basic function with comments

src/hotp.js

@@ -6,5 +6,47 @@
 import OTP from './otp';
 
 class HOTP extends OTP {
-    
+    /*＊
+     * Generate the OTP with the given count
+     *
+     * @param {count}
+     * @type {int} 
+     * @desc the OTP HMAC counter
+     *
+     * @return {OTP}
+     *
+     * @example
+     * ```javascript
+     * let hotp = jsotp.HOTP.gen('BASE32_ENCODED_SECRET');
+     * hotp.at(0); // => 432143
+     * ```
+     */
+    at(count) {
+        console.log("HOTP.at");
+    }
+
+    /*＊
+     * Verifies the OTP passed in against the current counter.
+     *
+     * @param {otp}
+     * @type {String} 
+     * @desc the OTP waiting for checking
+     *
+     * @param {counter}
+     * @type {int} 
+     * @desc the OTP HMAC counter
+     *
+     * @return {Boolean}
+     *
+     * @example
+     * ```javascript
+     * let hotp = jsotp.HOTP.gen('BASE32_ENCODED_SECRET');
+     * hotp.at(0); // => 432143
+     * hotp.verify(432143, 0); // => true
+     * hotp.verify(432143, 1); // => false
+     * ```
+     */
+    verify(otp, counter) {
+        console.log("HOTP.verify");
+    }
 }