Two minor docs fixes

[alessbell]

Description

Includes two fixes for minor docs issues I encountered:

• a syntax error when copying + pasting the template example in docs/themes.md
• a backwards ternary that just needed to be flipped (as I understand it)

I haven't created an issue but would be happy to. Thanks!

Type of Change

• [ ] 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 not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Checklist: (Feel free to delete this section upon completion)

• [ ] I have included a changeset if this change will require a version change to one of the packages.
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have run pnpm run check:ci and all checks pass
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] My changes generate no new warnings
• [ ] Any dependent changes have been merged and published in downstream modules