add link to manage subscription

Author: he-yang

source/profeatures.md

@@ -4,7 +4,7 @@
 
 The Excel-to-JSON add-in offers a set of pro features that enhance the functionality of the add-in. These features are only available to users who have subscribed the add-in.
 
-## Subscription
+## Subscription, Payment and Cancellation
 
 7 days free trial, then you will be charged monthly at one of the following rates for the Pro Features. You can cancel your subscription at any time before the 7th day, and you will not be charged:
 - USD US$2.66 / month,
@@ -17,7 +17,10 @@ Each Pro Code can offer 10 devices to access Pro Features.After the 7 day trial
 
 Each Pro code is valid for both Excel-to-JSON and [JSON-to-Excel](https://json-to-excel.wtsolutions.cn/en/latest/) add-in provided by WTSolutions.
 
-Subscribe through Stripe, here [https://buy.stripe.com/00gdQT2iz0Vp32E002](https://buy.stripe.com/00gdQT2iz0Vp32E002)
+### Subscribe through Stripe
+
+[https://buy.stripe.com/00gdQT2iz0Vp32E002](https://buy.stripe.com/00gdQT2iz0Vp32E002)
+
 Payment method:
 - Bank Card (Visa, Mastercard, American Express, JCB, 银联)
 - Apple Pay (needs to open the above link using your Apple/IOS/Mac Device)
@@ -26,6 +29,12 @@ Payment method:
 
 For subscription terms, kindly refer to the [Terms of Use](termsofuse.md)
 
+### Cancel Subcription
+
+You can cancel your subscription at any time. After the current billing cycle ends, you will no longer have access to the pro features.
+
+[https://billing.stripe.com/p/login/5kQ4gyadZ7p22JY3V83Je00](https://billing.stripe.com/p/login/5kQ4gyadZ7p22JY3V83Je00)
+
 ## Pro Code
 
 Pro Code is the `email address` you used during the checkout process of the Excel-to-JSON add-in on Stripe. This code is required to access pro features.