Support for Hardhat 3

[luispedro18]

Add Hardhat 3 support - Plugin system migration needed

Problem

The solidity-docgen package is currently incompatible with Hardhat 3 due to fundamental changes in how plugins and tasks are defined. This is currently blocking the migration of our project to version 3. According to the Hardhat 3 migration guide, Hardhat 3 introduced several breaking changes:

1. Declarative config: Plugins, tasks, and other extensions must be configured explicitly in the config instead of being registered by side effects
2. ESM-first: Hardhat config must be an ES module
3. Extensibility through hooks: Features like extendConfig and subtask overriding were replaced by the new hooks system

Current Error

When trying to use solidity-docgen with Hardhat 3, users encounter:

Error HHE404: Task "docgen" not found

This occurs because:

• The hardhat API structure changed significantly

Expected Behavior

solidity-docgen should work seamlessly with Hardhat 3 by:

1. Using the new declarative plugin system
2. Following the new hooks system for extending functionality

Proposed Solution

1. Implement declarative plugin: Create a proper plugin that can be added to the plugins array in hardhat.config.ts
2. Update documentation: Provide migration examples for users upgrading from Hardhat 2

Environment

• Hardhat version: 3.0.6
• solidity-docgen version: 0.6.0-beta.36
• Node.js version: 24.2.0