docs: add Uniblock to the RPC provider directory

Author: hkhiem8

cspell/project-words.txt

@@ -152,3 +152,4 @@ Hypernative
 Hypernative's
 predeterministic
 sfrx
+Uniblock

src/pages/tools/rpc.mdx

@@ -64,6 +64,14 @@ dRPC provides enterprise-level RPC infrastructure with globally distributed node
   [dRPC](https://drpc.org/chainlist/ink) works seamlessly with Ink and all Superchain networks.
 </Callout>
 
+## [Uniblock](https://uniblock.dev/chains/ink/?utm_source=ink-docs&utm_medium=ecosystem-docs&utm_campaign=ecosystem&utm_content=intro)
+
+Uniblock provides a unified JSON-RPC endpoint that routes requests across 55+ upstream providers with automatic failover.
+
+**Supported Networks**
+
+- Ink Mainnet
+- Ink Sepolia
 
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