Update README.md

README.md

 # Drone-Olfaction-Patterns
 This repository contains a database extracted during an experiment conduced in Wageningen University & Research. It is composed of multiple geographically labeled points with information about the nitrogen dioxide (NO2) content in the atmosphere as measured by an eletrical sensor attached to a UAV. A brief introduction can be seen in the following video:
 
-<iframe src="https://player.vimeo.com/video/471958082" width="640" height="360" frameborder="0" allow="autoplay; fullscreen" allowfullscreen></iframe>
+<figure class="video_container">
+    <iframe src="https://player.vimeo.com/video/471958082" width="640" height="360" frameborder="0" allow="autoplay; fullscreen" allowfullscreen></iframe>
+</figure>
 <p><a href="https://vimeo.com/471958082">MDPI_micromachines</a> from <a href="https://vimeo.com/user125797359">Jo&atilde;o Ot&aacute;vio</a> on <a href="https://vimeo.com">Vimeo</a>.</p>
 
 * **License**