Add specific page for rpc endpoints (#13899)

docs/src/cluster/rpc-endpoints.md

@@ -0,0 +1,20 @@
+---
+title: Solana Cluster RPC Endpoints
+---
+
+Solana maintains dedicated api nodes to fulfill [JSON-RPC](developing/clients/jsonrpc-api.md)
+requests for each public cluster, and third parties may as well. Here are the
+public RPC endpoints currently available and recommended for each public cluster:
+
+## Devnet
+
+- `https://devnet.solana.com` - single Solana-hosted api node; rate-limited
+
+## Testnet
+
+- `https://testnet.solana.com` - single Solana-hosted api node; rate-limited
+
+## Mainnet Beta
+
+- `https://api.mainnet-beta.solana.com` - Solana-hosted api node cluster, backed by a load balancer; rate-limited
+- `https://solana-api.projectserum.com` - Project Serum-hosted api node