feat: add snakefmt formatter for snakemake files (#399)

README.md

@@ -287,6 +287,7 @@ You can view this list in vim with `:help conform-formatters`
 - [shellharden](https://github.com/anordal/shellharden) - The corrective bash syntax highlighter.
 - [shfmt](https://github.com/mvdan/sh) - A shell parser, formatter, and interpreter with `bash` support.
 - [smlfmt](https://github.com/shwestrick/smlfmt) - A custom parser and code formatter for Standard ML.
+- [snakefmt](https://github.com/snakemake/snakefmt) - a formatting tool for Snakemake files following the design of Black.
 - [sql_formatter](https://github.com/sql-formatter-org/sql-formatter) - A whitespace formatter for different query languages.
 - [sqlfluff](https://github.com/sqlfluff/sqlfluff) - A modular SQL linter and auto-formatter with support for multiple dialects and templated code.
 - [sqlfmt](https://docs.sqlfmt.com) - sqlfmt formats your dbt SQL files so you don't have to. It is similar in nature to Black, gofmt, and rustfmt (but for SQL)

doc/conform.txt

@@ -327,6 +327,8 @@ FORMATTERS                                                    *conform-formatter
 `shellharden` - The corrective bash syntax highlighter.
 `shfmt` - A shell parser, formatter, and interpreter with `bash` support.
 `smlfmt` - A custom parser and code formatter for Standard ML.
+`snakefmt` - a formatting tool for Snakemake files following the design of
+           Black.
 `sql_formatter` - A whitespace formatter for different query languages.
 `sqlfluff` - A modular SQL linter and auto-formatter with support for multiple
            dialects and templated code.

lua/conform/formatters/snakefmt.lua

@@ -0,0 +1,10 @@
+---@type conform.FileFormatterConfig
+return {
+  meta = {
+    url = "https://github.com/snakemake/snakefmt",
+    description = "a formatting tool for Snakemake files following the design of Black.",
+  },
+  command = "snakefmt",
+  args = "$FILENAME",
+  stdin = false,
+}