Update README.md

Author: mooseburgr

README.md

@@ -15,3 +15,9 @@ _BUT_ if you do, you can use this Google Cloud Function to do this content massa
 Credit to the following packages doing about 99.9% of the work:
  - https://github.com/mmcdole/gofeed
  - https://github.com/arran4/golang-ical
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+
+## Rapid API
+
+Rapid API listing:
+https://rapidapi.com/kylejohnsonmn-7vy1VSLzbvA/api/rss-to-ical