feat: add fantomas formatter (#302)

* feat: add fantomas formatter

* fantomas: + args

* fantomas: + stdin = false

README.md

@@ -213,6 +213,7 @@ You can view this list in vim with `:help conform-formatters`
 - [erb_format](https://github.com/nebulab/erb-formatter) - Format ERB files with speed and precision.
 - [eslint_d](https://github.com/mantoni/eslint_d.js/) - Like ESLint, but faster.
 - [fish_indent](https://fishshell.com/docs/current/cmds/fish_indent.html) - Indent or otherwise prettify a piece of fish code.
+- [fantomas](https://github.com/fsprojects/fantomas) - F# source code formatter.
 - [fixjson](https://github.com/rhysd/fixjson) - JSON Fixer for Humans using (relaxed) JSON5.
 - [fnlfmt](https://git.sr.ht/~technomancy/fnlfmt) - A formatter for Fennel code.
 - [fourmolu](https://hackage.haskell.org/package/fourmolu) - Fourmolu is a formatter for Haskell source code.

lua/conform/formatters/fantomas.lua

@@ -0,0 +1,10 @@
+---@type conform.FileFormatterConfig
+return {
+  meta = {
+    url = "https://github.com/fsprojects/fantomas",
+    description = "F# source code formatter.",
+  },
+  command = "fantomas",
+  args = { "$FILENAME" },
+  stdin = false,
+}