jq

[osvadkovsky@lab1 blue]$  \
jq '.run_list = .run_list + ["recipe[saas-rsyslog8-forward]"]' wn2.blue.websaas.rnd.qa.json
{
  "chef_environment": "color",
  "name": "wn2.blue.websaas.rnd.qa",
  "normal": {
    "DataCenterNameInEnv": "blue",
    "tags": []
  },
  "run_list": [
    "role[saas_webnode_color]",
    "role[saas_cydns_color]",
    "role[color-eleven-base]",
    "role[blue-saas-logs-collector]",
    "recipe[saas-filebeat-color]",
    "recipe[collectd-ng]",
    "recipe[saas-rsyslog8-forward]"
  ]
}