docs: link OpenChainBench public Ink RPC latency benchmark

[Flotapponnier]

Summary

Adds a short subsection at the end of src/pages/tools/rpc.mdx (under the existing "Public Endpoints" section) linking to a public, multi-region latency benchmark of Ink's keyless RPC endpoints.

The goal is to give integrators an independent signal when choosing between the four public providers already documented on this page (Gelato, Tenderly, QuickNode, dRPC).

What it links to

OpenChainBench / ink-rpc — an open-source (ChainBench/openchainbench) probe run from Paris (eu-west), Virginia (us-east) and Singapore (ap-southeast). It:

• Calls eth_getBlockByNumber on each keyless provider every 60 seconds from all 3 regions.
• Publishes p50 / p95 wall-clock request latency and availability.
• Rolls up 24 h / 7 d / 30 d views with methodology and raw JSON.

No API keys, no signup, no paywall.

Why here

The "Public Endpoints" section lists the four keyless providers side by side with only marketing blurbs. A single-line reference to a neutral, open benchmark lets integrators compare them from their own region before committing.

Notes

• Diff is 6 lines, 1 file.
• The benchmark covers exactly the four keyless providers already listed here (Gelato rpc-gel, Tenderly rpc-ten, QuickNode rpc-qnd, dRPC ink.drpc.org).
• I am not affiliated with any of the providers on the benchmark; happy to reword if the phrasing reads as promotional.