Add foundry-sol extension

[Copernicium282]

Foundry-first Solidity language support for Zed.
Forked from zarifpour/zed-solidity.

What's included

• Syntax highlighting — tree-sitter grammar for .sol and .yul
• LSP — auto-installs @nomicfoundation/solidity-language-server for go-to-definition, hover, diagnostics, completions
• Foundry project detection — reads foundry.toml, resolves remappings via forge remappings
• 32 snippets — core Solidity patterns, ERC interfaces (ERC20/721/1155), NatSpec block templates
• Code outline — contracts, functions, events, errors in the symbol tree

Changes from upstream

• Added language_server_initialization_options for proper LSP server handshake
• Added 32 snippets (core patterns, ERC interfaces, NatSpec blocks)
• Added snippets key to extension.toml
• Documented forge fmt and cast source usage in README
• Documented known Hardhat config limitation with patch script

Testing

Tested as a dev extension with a Foundry project using chainlink-evm dependency:

• Go-to-definition works for remapped imports
• Snippets expand correctly
• LSP detects Foundry project and resolves remappings

Proof

Screencast_20260614_091815.webm