title: Insert character in Scala String
body: <p>For any given <code>String</code>, for instance</p>
  
  <pre><code>val s = "abde"
  </code></pre>
  
  <p>how to insert a character <code>c: Char</code> at position 2, after <code>b</code> ?</p>
  
  <p><strong>Update</strong> </p>
  
  <p>Which Scala collection to consider for multiple efficient insertions and deletions at random positions ? (Assuming that a <code>String</code> may be transformed into that collection.)</p>