chore: What is the process for setting up a whitelist to restrict modifications by the Mason CLI for specific files?

**Description**

I have created a custom template using Stencil. When I include this template under the "bricks" directory and use a specific brick, it automatically modifies the Stencil template without defining the variables in the brick.yaml file. How can I prevent this from happening?

**Here is brick.yaml file content**

```
name: boilerplate_brick
description: A new brick created with the Mason CLI.

vars:
project_name:
type: string
description: Provide your project name
default: SampleProject
prompt: What is your project name?

bundle_id:
type: string
description: Provide your project bundle id
default: com.example.sampleproject
prompt: What is your project bundle id?
```


**Here is the Stencil template**
```

// swiftlint:disable all
// Generated using SwiftGen — https://github.com/SwiftGen/SwiftGen
{% if catalogs %}
{% set enumName %}{{param.enumName|default:"Asset"}}{% endset %}
{% set forceNamespaces %}{{param.forceProvidesNamespaces|default:"false"}}{% endset %}
{% set accessModifier %}{% if param.publicAccess %}public{% else %}internal{% endif %}{% endset %}
{% macro enumBlock assets %}
{% call casesBlock assets %}
{% endmacro %}
{% macro casesBlock assets %}
{% for asset in assets %}
{% if asset.type == "color" %}

static var {{asset.name|swiftIdentifier:"pretty"|lowerFirstWord|escapeReservedKeywords}}: UIColor {
return {{enumName}}.Colors.{{asset.name|swiftIdentifier:"pretty"|lowerFirstWord|escapeReservedKeywords}}.color
}
{% elif asset.items and ( forceNamespaces == "true" or asset.isNamespaced == "true" ) %}
{% call casesBlock asset.items %}
{% elif asset.items %}
{% call casesBlock asset.items %}
{% endif %}
{% endfor %}
{% endmacro %}

import UIKit

// swiftlint:disable identifier_name line_length nesting type_body_length type_name
{{accessModifier}} extension UIColor {
{% if catalogs.count > 1 or param.forceFileNameEnum %}
{% for catalog in catalogs %}
{% call enumBlock catalog.assets %}
{% endfor %}
{% else %}
{% call enumBlock catalogs.first.assets %}
{% endif %}
}
// swiftlint:enable identifier_name line_length nesting type_body_length type_name

{% else %}
// No assets found
{% endif %}
```

**Updated the Stencil template by Mason CLI**

```
// swiftlint:disable all
// Generated using SwiftGen — https://github.com/SwiftGen/SwiftGen
{% if catalogs %}
{% set enumName %}{% endset %}
{% set forceNamespaces %}{% endset %}
{% set accessModifier %}{% if param.publicAccess %}public{% else %}internal{% endif %}{% endset %}
{% macro enumBlock assets %}
{% call casesBlock assets %}
{% endmacro %}
{% macro casesBlock assets %}
{% for asset in assets %}
{% if asset.type == "color" %}

static var : UIColor {
return .Colors..color
}
{% elif asset.items and ( forceNamespaces == "true" or asset.isNamespaced == "true" ) %}
{% call casesBlock asset.items %}
{% elif asset.items %}
{% call casesBlock asset.items %}
{% endif %}
{% endfor %}
{% endmacro %}

import UIKit

// swiftlint:disable identifier_name line_length nesting type_body_length type_name
extension UIColor {
{% if catalogs.count > 1 or param.forceFileNameEnum %}
{% for catalog in catalogs %}
{% call enumBlock catalog.assets %}
{% endfor %}
{% else %}
{% call enumBlock catalogs.first.assets %}
{% endif %}
}
// swiftlint:enable identifier_name line_length nesting type_body_length type_name

{% else %}
// No assets found
{% endif %}

```

**Requirements**
The Mason CLI should refrain from modifying the Stencil template unless the variables are defined in the brick.yaml file.