Add .NET Core library link

pages/index.tmpl

@@ -28,6 +28,7 @@
 				<ul>
 					<li><a href="https://github.com/writeas/go-writeas">Go</a></li>
 					<li><a href="https://github.com/writeas/writefreely-swift">Swift</a> (WriteFreely)</li>
+					<li><a href="https://github.com/DinoBansigan/WriteAs.NET">.NET Core</a></li>
 					<li><a href="https://github.com/devsnek/writeas.js">Javascript</a></li>
 					<li><a href="https://github.com/cjeller1592/WriteasAPI">Python</a></li>
 					<li><a href="https://github.com/theimpossibleastronaut/writeas.php">PHP</a></li>