title: How to expand list which contains multiple dictionaries into a dataframe?
body: <p>I need to expand list with multiple dictionaries but really cant find the way...</p>
  <p>This is how df looks:</p>
  <pre><code>ColumnA       actions
  A             [{'link_click': '1'}, {'post_engagement': '1'}]
  B             [{'link_click': '13'}, {'post_engagement': '5'}, {'page_engagement': '7'}]
  </code></pre>
  <p>This is how my desired output should be:</p>
  <pre><code> ColumnA          actions_Link_click       actions_post_engagement      actions_page_engagement
      A                 1                          1                              na
      B                 13                         5                              7
  </code></pre>