docs: add BoltRPC to Base node providers

[KubilayJackson]

What changed? Why?

Adds BoltRPC to the Base node providers page with a link to its Base RPC offering and a short summary of HTTPS/WebSocket access, multi-chain API key model, and pricing.

Notes to reviewers

• Entry follows the existing provider listing format.
• Links:
  • https://boltrpc.io/
  • https://boltrpc.io/networks/base
  • https://boltrpc.io/pricing
• Supported networks listed: Base Mainnet (chain ID 8453).
• Docs-only change; does not modify Base network configuration.

How has it been tested?

• Verified Base Mainnet product page and endpoint docs at https://boltrpc.io/networks/base
• Documentation-only change

[cb-heimdall]

🟡 Heimdall Review Status

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Reviews	🟡 0/2 Emergency override progress: 0/5 These approvals do not satisfy normal or CODEOWNER requirements because the commit identity is unverified.	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 1 Sum 2