How to add IAM Trust Relationship to default role

Is there any way to add an additional IAM trust relationship to the default role created by serverless? Specifically, I’d like to add the following policy to the default role. Any help is greatly appreciated!

{
“Version”: “2012-10-17”,
“Statement”: [
{
“Effect”: “Allow”,
“Principal”: {
“Service”: “medialive.amazonaws.com
},
“Action”: “sts:AssumeRole”
}
]
}

Possible solution: https://gist.github.com/sdomagala/a647a69f0dd87af545d7c45dfc7b0114