feat: add support for rumdl fmt (#840)

* feat(tools): add support for rumdl fmt

* refactor: format stdin

Author: hougesen

README.md

@@ -366,6 +366,7 @@ You can view this list in vim with `:help conform-formatters`
 - [ruff_format](https://docs.astral.sh/ruff/) - An extremely fast Python linter, written in Rust. Formatter subcommand.
 - [ruff_organize_imports](https://docs.astral.sh/ruff/) - An extremely fast Python linter, written in Rust. Organize imports.
 - [rufo](https://github.com/ruby-formatter/rufo) - Rufo is an opinionated ruby formatter.
+- [rumdl](https://github.com/rvben/rumdl) - Markdown Linter and Formatter written in Rust.
 - [runic](https://github.com/fredrikekre/Runic.jl) - Julia code formatter.
 - [rustfmt](https://github.com/rust-lang/rustfmt) - A tool for formatting rust code according to style guidelines.
 - [rustywind](https://github.com/avencera/rustywind) - A tool for formatting Tailwind CSS classes.

doc/conform.txt

@@ -517,6 +517,7 @@ FORMATTERS                                                    *conform-formatter
 `ruff_organize_imports` - An extremely fast Python linter, written in Rust.
                         Organize imports.
 `rufo` - Rufo is an opinionated ruby formatter.
+`rumdl` - Markdown Linter and Formatter written in Rust.
 `runic` - Julia code formatter.
 `rustfmt` - A tool for formatting rust code according to style guidelines.
 `rustywind` - A tool for formatting Tailwind CSS classes.

lua/conform/formatters/rumdl.lua

@@ -0,0 +1,10 @@
+---@type conform.FileFormatterConfig
+return {
+  meta = {
+    url = "https://github.com/rvben/rumdl",
+    description = "Markdown Linter and Formatter written in Rust.",
+  },
+  command = "rumdl",
+  args = { "fmt", "-" },
+  stdin = true,
+}