doc: document we have the ci/ scripts

Signed-off-by: Stewart Smith <stewart@linux.ibm.com>
diff --git a/doc/process/index.rst b/doc/process/index.rst
index a8443ba..4efe358 100644
--- a/doc/process/index.rst
+++ b/doc/process/index.rst
@@ -5,3 +5,4 @@
 
    CONTRIBUTING.md
    KernelTree.rst
+   building-with-ci