Add debug logs to mermaid iframe

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 6a679d0f3bc73ac89aac9aa66078b2d8d70b73b2

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | ---------------------------- | ----- | | @gitbook/integration-mermaid | Patch |

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR