Document the release process

An initial document describing the mechanics of how a release is made.
This is a start of documenting our full development process.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/docs/index.md b/docs/index.md
index e31b415..ca08c72 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -25,6 +25,7 @@
 - Testing
   - The [Zephyr]({% link testplan-zephyr.md %}) test plan.
   - The [mynewt]({% link testplan-mynewt.md %}) test plan.
+- Our [release process]({% link release.md %}).
 
 There is also a document about [signed images]({% link
 signed_images.md %}) that is out of date.  You should use `imgtool.py`