Merge branch 'releasev1.4.0' into 'develop'

Release v1.4.0

See merge request oai/cn5g/oai-cn5g-upf-vpp!30

CHANGELOG.md

 # RELEASE NOTES: #
 
+## v1.4.0 -- July 2022 ##
+
+* Standalone support validated for traffic steering and redirection
+* Added instructions for bare-metal installation
+* Support for Ubuntu 20.04 bare-metal/docker installation
+* Official images produced by CI are pushed to `oaisoftwarealliance` Docker-Hub Team account
+
 ## v1.3.0 -- January 2022 ##
 
 * Upgrade to UPG plugin stable/1.2

README.md

@@ -15,6 +15,7 @@ At the moment, it contains the following network elements:
 * Unified Data Management (**UDM**)
 * Unified Data Repository (**UDR**)
 * User Plane Function (**UPF**)
+* Network Slicing Selection Function (**NSSF**)
 
 Each has its own repository: this repository (`oai-cn5g-upf-vpp`) is meant for UPF.