title: Pandas - Add seconds from a column to datetime in other column
body: <p>I have a dataFrame with two columns, <code>["StartDate" ,"duration"]</code> 
  the elements in the <code>StartDate</code> column are <code>datetime</code> type, and the <code>duration</code> are ints. </p>
  
  <p>Something like: </p>
  
  <pre><code>StartDate  Duration
  08:16:05    20  
  07:16:01    20
  </code></pre>
  
  <p>I expect to get: </p>
  
  <pre><code>EndDate 
  08:16:25
  07:16:21
  </code></pre>
  
  <p>Simply add the seconds to the hour. </p>
  
  <p>I'd being checking some ideas about it like the delta <a href="https://pandas.pydata.org/pandas-docs/stable/timedeltas.html" rel="noreferrer">time types</a> and that all those datetimes have the possibilities to add delta times, but so far I can find how to do it with the DataFrames (in a vector fashion, cause It might be possible to iterate over all the rows performing the operation ). </p>