fix(keyboard): add '&' character

src/extra/widgets/keyboard/lv_keyboard.c

@@ -73,7 +73,7 @@ static const lv_btnmatrix_ctrl_t default_kb_ctrl_uc_map[] = {
 };
 
 static const char * const default_kb_map_spec[] = {"1", "2", "3", "4", "5", "6", "7", "8", "9", "0", LV_SYMBOL_BACKSPACE, "\n",
-                                                   "abc", "+", "-", "/", "*", "=", "%", "!", "?", "#", "<", ">", "\n",
+                                                   "abc", "+", "&", "/", "*", "=", "%", "!", "?", "#", "<", ">", "\n",
                                                    "\\",  "@", "$", "(", ")", "{", "}", "[", "]", ";", "\"", "'", "\n",
                                                    LV_SYMBOL_KEYBOARD, LV_SYMBOL_LEFT, " ", LV_SYMBOL_RIGHT, LV_SYMBOL_OK, ""
                                                   };