Adding AppOptics storage adapter (prometheus#937)

Author: leecalcote

content/docs/operating/integrations.md

@@ -32,6 +32,7 @@ is primarily intended for long term storage. It is recommended that you perform
 careful evaulation of any solution in this space to confirm it can handle your
 data volumes.
 
+  * [AppOptics](https://github.com/solarwinds/prometheus2appoptics): write
   * [Chronix](https://github.com/ChronixDB/chronix.ingester): write
   * [Cortex](https://github.com/weaveworks/cortex): read and write
   * [CrateDB](https://github.com/crate/crate_adapter): read and write