rpc_api.md: add .proc_get_config

Summary

• style.css: set custom bullets for nested lists
• rpc_api.md: add .proc_get_config

Address changes from:

• picodata@b7b01ab4 — .proc_get_config implementation
• picodata@af8647c7 — add pg option
• picodata@9f0d4503 — rename tiers -> tier, peers -> peer

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• Close #258 (closed)
• Cherry-pick to: 24.4
• Staging: https://docs.binary.picodata.io/picodata/asabirov_add_proc_get_config/architecture/rpc_api/#.proc_get_config