exporters: add OpenChainBench blockchain RPC exporter

[Flotapponnier]

Adds OpenChainBench to the Miscellaneous exporters list, placed alphabetically between Open OnDemand and OpenClaw.

What it exports: blockchain RPC provider health metrics — request latency (p50/p95/p99), reliability classification, stale-block detection, and gas oracle accuracy across 22 EVM chains and Solana. Each harness is a Go binary exposing a standard /metrics endpoint built with github.com/prometheus/client_golang.

Repo: https://github.com/ChainBench/OpenChainBench (Apache-2.0)

Sample metric names: ocb_rpc_latency_seconds, ocb_rpc_reliability_class, ocb_stale_block_lag_blocks, ocb_gas_oracle_error_ratio.

Disclosure: I contribute to the project. Happy to reword the entry, drop it, or move it to the "Software exposing Prometheus metrics" section if that fits better — the harnesses are also runnable as a hosted service that exposes /metrics directly.

[jan--f]

Hello from the bug scrub!
Thank you for your contribution. I'm afraid we need to decline this for now. We are happy to feature exporters that are actively developed and used. Unfortunately this one has so far only a limited community behind it and seemingly low adoption. Please try again at a later stage.