[Feature] Possibility to define where the theme change button appears: (docs, canvas or both)

[dgateles]

Describe the feature

When using withThemeByDataAttribute, it happens to apply the theme also to the Docs (mdx), causing in some circumstances the examples to break (apply dark theme and the background remains light). Thinking about it, it would be interesting to be able to define where this theme will be applied and also the possibility of saying where the theme exchange button should appear.