title: Add custom functionalities to Doxygen
body: <p>I'm working on my project which uses Doxygen, and I need to implement a custom Google search bar and a drop-down of versions like what OpenCV has on their documentation page <a href="https://docs.opencv.org/master/" rel="nofollow noreferrer">here</a>.</p>
  
  <p><a href="https://i.stack.imgur.com/oKKn1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/oKKn1.png" alt="enter image description here"></a></p>
  
  <p>I searched through the code on their Github <a href="https://github.com/opencv/opencv" rel="nofollow noreferrer">repo</a>, but I couldn't find a place where those are implemented.</p>
  
  <p>Doxygen's documentation <a href="http://www.doxygen.nl/manual/index.html" rel="nofollow noreferrer">page</a> doesn't have anything on this either, and I couldn't find an answer anywhere else.</p>
  
  <p>Does anyone have an idea on how to do this?</p>
  
  <p>Thanks. </p>