Doc: add release process description

Extend the document with information about how releases are made.

Change-Id: I145f195d4f523e9335abf60bdf2e4245aa2d737c
Signed-off-by: Gyorgy Szing <Gyorgy.Szing@arm.com>
diff --git a/docs/project/index.rst b/docs/project/index.rst
index 83f493f..d7a4b4b 100644
--- a/docs/project/index.rst
+++ b/docs/project/index.rst
@@ -14,6 +14,7 @@
     versioning_policy
     version_control
     quality-assurance/index
+    releases
 
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