Add SuprSend

adding suprsend inside messaging category, which has a generous free tier for devs.

Author: nik-l9

README.md

@@ -805,6 +805,7 @@ This list results from Pull Requests, reviews, ideas, and work done by 1600+ peo
   * [httpSMS](https://httpsms.com) - Send and receive text messages using your Android phone as an SMS Gateway. Free to send and receive up to 200 messages per month.
   * [EMQX Serverless](https://www.emqx.com/en/cloud/serverless-mqtt) - Scalable and secure serverless MQTT broker you can get in seconds. 1M session minutes/month free forever (no credit card required).
   * [Pocket Alert](https://pocketalert.app) - Send push notifications to your iOS and Android devices. Effortlessly integrate via API or Webhooks and maintain full control over your alerts. Free plan: 50 messages per day to 1 device and 1 application.
+  * [SuprSend](https://www.suprsend.com/) - SuprSend is a notification infrastructure that streamlines your product notifications with an API-first approach. Create and deliver transactional, crons, and engagement notifications on multiple channels with a single notification API. You can try out SuprSend APIs from their [Postman collection](https://www.postman.com/suprsend/workspace/suprsend/collection/27786422-d77a13c1-8f59-406d-9669-078a10d52521)
 
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