chore(version 3.2): update docs for theme migration

[rileylnapier]

Description

version 3.2

Type of change

• [ ] Bug fix (non-breaking change that fixes an issue)
• [ ] New feature (non-breaking change that adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Related issues

Fix [#1]()

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (main@7e3387a). Click here to learn what that means. Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #417 +/- ## ======================================= Coverage ? 36.13% ======================================= Files ? 68 Lines ? 1093 Branches ? 307 ======================================= Hits ? 395 Misses ? 698 Partials ? 0 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trycourier). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trycourier)

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