dsh-fmt: Formatting and Validating JSON, YAML, TOML, and SQL Text

`dsh-fmt` is a DSH plugin maintained by ZhijiangTang, providing the `format_text` tool for formatting and validating JSON, YAML, TOML, and SQL text. The plugin is a pure ESM module with no build dependencies. It requires `text` and `format` parameters when invoked and supports custom indentation, SQL dialect, and keyword case. The tool returns a well-formed JSON value containing either the formatted result or error information (including location), and parsing failures do not interrupt the workflow.