Adding credentials to pull from docker repository

pipeline.yml

@@ -8,6 +8,8 @@ resource_types:
     type: docker-image
     source:
       repository: nexus.nulloctet.com:5000/sothr/matrix-notification-resource
+      username: ((nexus_docker_read.username))
+      password: ((nexus_docker_read.password))
 
 resources:
   - name: git-develop