only send format editings when necessary

If the original document is same as the formatted one, there's no need to send the unchanged
document's content back which will make the client confused.

Signed-off-by: Tw <tw19881113@gmail.com>

src/main.zig

@@ -1650,6 +1650,8 @@ fn formattingHandler(arena: *std.heap.ArenaAllocator, id: types.RequestId, req:
 
         switch (try process.wait()) {
             .Exited => |code| if (code == 0) {
+                if (std.mem.eql(u8, handle.document.text, stdout_bytes)) return try respondGeneric(id, null_result_response);
+
                 return try send(arena, types.Response{
                     .id = id,
                     .result = .{