Storybook: preview-head.html not used in docs page iframe in Storybook 6

[mattschloss]

Is your feature request related to a problem? Please describe.
In Storybook 5, we were able to use preview-head.html to define custom styles on the docs page. This was needed to fix a conflict for the background-color of code previews.

Describe the solution you'd like
Provide a way to inject custom styles into the docs page iframe.

Describe alternatives you've considered
Setting docs theme to light or dark doesn't change the code preview styles. The current alternative is to add a class to our application/library's css.

Are you able to assist bring the feature to reality?
no

Additional context

[shilman]

@mattschloss I think this is a bug. What version are you upgrading from?

[mattschloss]

I upgraded from version 5.3.19

[stale[bot]]

Hi everyone! Seems like there hasn't been much going on in this issue lately. If there are still questions, comments, or bugs, please feel free to continue the discussion. Unfortunately, we don't have time to get to every issue. We are always open to contributions so please send us a pull request if you would like to help. Inactive issues will be closed after 30 days. Thanks!

[parash-namespace]

preview-body seems to work rather than preview-head with version 6.0.26. preview-body fixed it for me.