Add Monad to the Docs on Substreams.dev

[codegen-sh]

This PR adds Monad Mainnet support to the Substreams documentation, following the same pattern as the NEAR integration (BLO-731).

Changes Made

New Tutorial

• Created docs/new/tutorials/monad.md with comprehensive Monad tutorial
• Includes warning box about eth_calls limitation due to Monad full nodes not providing access to arbitrary historic state
• References official Monad documentation: https://docs.monad.xyz/developer-essentials/historical-data#state

Documentation Updates

• Added Monad to docs/SUMMARY.md navigation structure
• Added Monad to docs/new/tutorials/intro-to-tutorials.md chain list
• Added Monad protobuf model and endpoint to docs/new/references/chains-and-endpoints.md

Key Features

• Uses EVM-compatible sf.ethereum.type.v2.Block protobuf model
• Provides Monad Mainnet endpoint: mainnet.monad.streamingfast.io:443
• Includes prominent warning about eth_calls unsupported functionality
• References Substreams Ethereum development kit for EVM compatibility

Resolves BLO-758

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💻 View my work • 👤 Initiated by Josh Kauffman • About Codegen
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[joshkauffman]

In the file: /chains-and-endpoints.md, the endpoint for monad should be mainnet-base.monad.streamingfast.io:443

Thanks for the heads up! I'll review and update the endpoint as needed. 📝

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[joshkauffman]

In the file monad.md, the endpoint for Monad on line 50 should be changed be mainnet-base.monad.streamingfast.io:443

I'll update the endpoint in monad.md as requested! 📝

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