Kernel+LibKeyboard: Store the keymap name when setting system keymap

This way we can query the kernel to see which keymap is currently in use.

Libraries/LibKeyboard/CharacterMap.h

@@ -43,9 +43,13 @@ public:
 
     u32 get_char(KeyEvent);
     void set_character_map_data(CharacterMapData character_map_data);
+    void set_character_map_name(const String& character_map_name);
+
+    const String character_map_name();
 
 private:
     CharacterMapData m_character_map_data;
+    String m_character_map_name;
 };
 
 }