feat: add csharp formatting

lua/plugins/formatting.lua

@@ -0,0 +1,19 @@
+return {
+    "stevearc/conform.nvim",
+    opts = {
+        formatters_by_ft = {
+            cs = { "csharpier" },
+        },
+        formatters = {
+            csharpier = {
+                command = "csharpier",
+                args = { "format", "--stdin-path", "$FILENAME" },
+                stdin = true,
+            },
+        },
+        format_on_save = {
+            timeout_ms = 3000,
+            lsp_fallback = true,
+        },
+    },
+}