feat: add ENULS mainnet

[Zhangnong]

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PR-Codex overview

This PR introduces support for the ENULS Mainnet in the codebase, adding it to the list of available blockchain definitions.

Detailed summary

• Added entry for ENULS Mainnet in the .changeset/great-pens-smash.md file.
• Exported enuls from src/chains/index.ts.
• Created enuls.ts in src/chains/definitions/ with details such as:
  • id: 119
  • nativeCurrency: NULS with 18 decimals
  • rpcUrls: default HTTP endpoint
  • blockExplorers: default explorer details
  • testnet: false

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[changeset-bot]

🦋 Changeset detected

Latest commit: 601d228

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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viem	Patch

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