Fix issue with custom fonts preview

[mr-vara]

Proposed changes

In SiteGen customisation step, the custom fonts are not getting reflected in the preview. This PR will ensure that the fonts selected are always reflected in the preview.

Type of Change

• Bugfix (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 not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• Linting and tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)