Update skills.html

Author: gokulsatya

skills.html

@@ -27,6 +27,7 @@
 						<li><a href="internships.html">Work Experience</a></li>
 						<li><a href="volunteer.html">Volunteer Experience</a></li>
 						<li><a href="projects.html">Projects</a></li>
+						<li><a href="Certifications.html">Certifications</a></li>
 						<li><a href="skills.html">Skills</a></li>
 					</ul>
 				</nav>