How can I add a list of fields?

Elastic Stack Logstash
1

I know how to use mutate add_field to add a field.
I know how to use mutate add_tag to add to [tags].
Is there any way to add a list of fields with structure?

I'd like to add something like this to the top-level json

"contexts":[
{
"type": "link",
"href": "http://www.example.com"
},
{
"type": "image",
"src": "www.example.com/logo.gif"
}
]