Created Debug with serial (markdown)

Debug-with-serial.md

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+You can only print things to debug for this.
+If you wanna set break point etc, use another debug method.
+
+# usage
+1. Include the async msg header in your file
+``` 
+
+#include "usb_serial_debug_bridge.hpp"
+
+``` 
+
+2 print things in your code and it will appear on serial.
+``` 
+void FileManBaseView::push_dir(const fs::path& path) {
+    std::string test_string = "test string:";
+    UsbSerialAsyncmsg::asyncmsg(test_string);
+    std::string test_string111 = "abcdefghi";
+    UsbSerialAsyncmsg::asyncmsg(test_string111);
+
+    std::string test_path_label = "test_path:";
+    UsbSerialAsyncmsg::asyncmsg(test_path_label);
+    UsbSerialAsyncmsg::asyncmsg(path);
+
+    std::string test_vec_label = "test_vector:";
+    UsbSerialAsyncmsg::asyncmsg(test_vec_label);
+
+    std::vector<uint32_t> test_vector;
+    test_vector.push_back(1);
+    test_vector.push_back(2);
+    test_vector.push_back(3);
+    UsbSerialAsyncmsg::asyncmsg(test_vector);
+
+    std::string test_num_label = "test_num:";
+    UsbSerialAsyncmsg::asyncmsg(test_num_label);
+
+    uint8_t test = 254;
+    UsbSerialAsyncmsg::asyncmsg(test);
+
+    if (path == parent_dir_path) {
+        pop_dir();
+    } else {
+        current_path /= path;
+        saved_index_stack.push_back(menu_view.highlighted_index());
+        menu_view.set_highlighted(0);
+        reload_current(true);
+    }
+}
+``` 
+
+# why not printing anything?
+* make sure async msg lock is disabled.
+``` 
+asyncmsg enable
+``` 
+* make sure serial connected
+``` 
+help
+``` 
+* MayhemHub currently not support real-time serial command communication. Use others.