feat: template generators

[mikemimik]

Description

Motivation and Context

• Feature Request: Update template plugin configuration property to be either a string or file path #1243
• We want more control over the mustache templates that are used

How Has This Been Tested?

• Manually tested using the demo/ package
  • Added example usage to the configuration

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes if appropriate.
• All new and existing tests passed.