added readme links

packages/medusa-payment-stripe/README.md

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+# medusa-payment-stripe
+
+Add Stripe as a Payment Provider.
+
+Learn more about how you can use this plugin in the [documentaion](https://docs.medusajs.com/add-plugins/stripe).
+
+## Options
+
+```js
+{
+  api_key: STRIPE_API_KEY,
+  webhook_secret: STRIPE_WEBHOOK_SECRET,
+}
+```