feat: support gluon fmt (nvim-lua#473)

Author: hougesen

lua/conform/formatters/gluon_fmt.lua

@@ -0,0 +1,10 @@
+---@type conform.FileFormatterConfig
+return {
+  meta = {
+    url = "https://github.com/gluon-lang/gluon",
+    description = "Code formatting for the gluon programming language.",
+  },
+  command = "gluon",
+  args = { "fmt", "$FILENAME" },
+  stdin = false,
+}