Add support for Zig

[jedisct1]

This adds Zig to the set of languages supported by code-context, simply by leveraging tree-sitter-zig.

[Shawnzheng011019]

@jedisct1 Hello! Thanks for your PR. But we've identified an issue:
Since the vscode-extension must run in a sandbox environment, you'll need to find out if there's a tree-sitter dependency package in Wasm format to ensure compatibility with the sandbox. This will also maintain consistency between MCP and the VS Code extension.
If you find a suitable Wasm package, please place it in the packages/vscode-extension/wasm directory and then re-run pnpm install && pnpm build. Afterward, test it using the methods outlined in packages/vscode-extension/CONTRIBUTING.md. If there are no issues, feel free to resubmit your PR.
We look forward to your updated submission!