通过行向彼此添加dataframes，保留R中的所有列

I have 3 dataframes that I would like to bind together by row but also retain the columns that each one has such that columns not present in one dataframe are just initialized to NA and added to the resultant dataframe. Since I may have many more columns than the ones provided in the example below, I can't hardcode them as I have been doing so far.I have 3 dataframes that I would like to bind t