env/corellium: add README.md pointing to the Corellium dashboard

Add Zenly contact as well.

Change-Id: Id4cb32c010caad8a3ec0f7124196db06e95f900c
Reviewed-on: https://go-review.googlesource.com/c/build/+/249358
Run-TryBot: Elias Naur <mail@eliasnaur.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/env/corellium/README.md b/env/corellium/README.md
new file mode 100644
index 0000000..4cf9068
--- /dev/null
+++ b/env/corellium/README.md
@@ -0,0 +1,12 @@
+Builders running on the [Corellium](https://corellium.com/)
+The ios and android directories contain scripts and supporting files
+for setting up a newly created virtual device.
+The current builders run on the https://go.corellium.com account,
+kindly provided by [Zenly](https://zen.ly/). Contact: steeve@zen.ly.
+New devices are set up through the Corellium
+[dashboard](https://go.corellium.com). Stuck devices are reset through
+the dashboard as well.