Add Validation Cloud to rpc-endpoints.md

Author: dan-kazenoff-vcc

docs/pos/reference/rpc-endpoints.md

@@ -117,5 +117,6 @@ Public RPCs may have rate limits or traffic restrictions. For dedicated free RPC
 - [1RPC](https://1rpc.io/)
 - [4EVERLAND](https://docs.4everland.org/rpc-beta/polygon)
 - [SubQuery](https://subquery.network/rpc)
+- [Validation Cloud](https://app.validationcloud.io)
 
 For a complete list of public endpoints, visit [Alchemy's Chain Connect](https://www.alchemy.com/chain-connect/chain/polygon-pos) and [Chainlist](https://chainlist.org/?search=Polygon+Mainnet).