content: mention Open Nebula integration

Added a link for the Firecracker Open Nebula integration, and reworded
the integration paragraph.

Author: raduweiss

index.html

@@ -96,14 +96,17 @@
               Kata Containers
             </a>
             ,
+            <a href="https://opennebula.io/firecracker/">Open Nebula</a>, 
+            <a href="https://github.com/solo-io/unik">UniK</a>,
             <a href="https://www.weave.works/oss/firekube/">Weave FireKube</a>
             (via
             <a href="https://github.com/weaveworks/ignite">Weave Ignite</a>
-            ), and containerd via
+            ),
+            and containerd via
             <a href="https://github.com/firecracker-microvm/firecracker-containerd">firecracker-containerd</a>
-            . It's also available within the
-            <a href="https://github.com/solo-io/unik">UniK</a>
-            unikernel and microVM platform. Firecracker can run Linux and
+            It's also used by
+            <a href="https://fly.io/">fly.io</a>
+            . Firecracker can run Linux and
             <a href="http://blog.osv.io/blog/2019/04/19/making-OSv-run-on-firecraker">OSv</a>
             guests. Our latest roadmap can be found
             <a href="https://github.com/firecracker-microvm/firecracker/projects/13">here</a>