Add NanoStack to Web3 as a service section

[0xerodev]

What

Adds NanoStack to the Web3 as a service section.

Entry

* [NanoStack](https://github.com/nano-labs-io/nanostack-api) - Permissionless cross-chain execution API — 59 chains, 8-15 bps fees, real-time signal data with BLAKE3 proofs.

Why it fits

• Permissionless Web3 infrastructure — no API key required, no gatekeeping
• Covers 59 chains: BTC, EVM (ETH/Base/ARB/OP), Solana, Cosmos, Polkadot, XRP, Cardano, and more
• Drop-in execution layer for dapps that need native cross-chain transactions
• Real-time signal data with BLAKE3 proofs for verifiable receipts

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