fix: Declare brick.yaml variable as a list of strings

**Description**

I'd like to configure one of my brick variables to be a list of strings. I'd like to provide a default value for that list in brick.yaml.

```yaml
vars:
some_list_var:
type: array
description: Some description
default:
- This is the default option
prompt: What items do you want?
```

**Expected Behavior**

I'm prompted for a list of values, with the default set to what configuration in the brick.yaml file.

**Actual behavior**

I get an error when running mason.

**Screenshots**

In this case, the variable is named "copyright_holders"