Add “CNCF” to glossary (#14537)

* Add glossary entry for CNCF

* Use CNCF glossary entry

content/en/docs/reference/glossary/cncf.md

@@ -0,0 +1,23 @@
+---
+title: Cloud Native Computing Foundation (CNCF)
+id: cncf
+date: 2019-05-26
+full_link: https://cncf.io/
+short_description: >
+  Cloud Native Computing Foundation
+
+aka:
+tags:
+- community
+---
+ The Cloud Native Computing Foundation (CNCF) builds sustainable ecosystems and
+ fosters a community around [projects](https://www.cncf.io/projects/) that
+ orchestrate containers as part of a microservices architecture.
+
+Kubernetes is a CNCF project.
+
+<!--more-->
+
+The CNCF is a sub-foundation of [the Linux Foundation](https://www.linuxfoundation.org/).
+Its mission is to make cloud native computing ubiquitous.
+