title: Put a character in between every character of all strings in a cell-array
body: <p>I have <code>input-cell = {'ABCD', 'ABD', 'BCD'}</code>. How can I put the operator <code>&lt;</code> into the strings in input-cell? </p>
  
  <p>The expected output should be:</p>
  
  <pre><code> output-cell = {'A&lt;B&lt;C&lt;D', 'A&lt;B&lt;D', 'B&lt;C&lt;D'}
  </code></pre>