Add appreciation to JetBrains

They provide us free licences and asked us to acknowledge that.

Author: mkurz

app/views/index.scala.html

@@ -304,6 +304,17 @@ <h3>Thank you to our premium sponsors!</h3>
                 <h3>Thank you to all our backers!</h3>
                 @renderBackers(backers)
             </div>
+            <h3>Thank you for providing free tooling!</h3>
+            <div class="flex-grid two-up three-up-medium three-up-large">
+                <div class="box block-only-not-small"></div>
+                <div class="box">
+                    <a href="//jetbrains.com/" target="_blank" rel="noopener noreferrer">
+                        <img src="https://resources.jetbrains.com/storage/products/company/brand/logos/jetbrains.png">
+                        <span></span>
+                    </a>
+                </div>
+                <div class="box block-only-not-small"></div>
+            </div>
         </article>
     </section>
     <script type="text/javascript" charset="utf-8" src="@routes.Assets.versioned("javascripts/fse.js")"></script>