feat: add opentofu-fmt formatter (#136)

Author: pimvh

lua/null-ls/builtins/formatting/opentofu_fmt.lua

@@ -0,0 +1,23 @@
+local h = require("null-ls.helpers")
+local methods = require("null-ls.methods")
+
+local FORMATTING = methods.internal.FORMATTING
+
+return h.make_builtin({
+    name = "opentofu_fmt",
+    meta = {
+        url = "https://opentofu.org/docs/cli/commands/fmt/#usage",
+        description = "The opentofu-fmt command rewrites `opentofu` configuration files to a canonical format and style.",
+    },
+    method = FORMATTING,
+    filetypes = { "terraform", "tf", "terraform-vars" },
+    generator_opts = {
+        command = "tofu",
+        args = {
+            "fmt",
+            "-",
+        },
+        to_stdin = true,
+    },
+    factory = h.formatter_factory,
+})