title: merge arrays in bigquery that have one common value
body: <p>In big query I have a table with one column with is an array of strings.
  The data will look like this : </p>
  
  <pre><code>['a','b']
  ['b','c']
  ['c', 'd']
  ['e']
  </code></pre>
  
  <p>Now my desired output is : </p>
  
  <pre><code>['a','b','c','d']
  ['e']
  </code></pre>
  
  <p>Basically I want to merge all the array that have at least one value in common. </p>
  
  <p>Any way I can do that?</p>
  
  <p>thanks</p>