Checklist

• I have searched the existing issues for similar feature requests.
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Summary

We currently have a command to show something in an iframe as part of st.components.v1.iframe. Since we just released custom components v2, we want to move away from the v1 API. I think it makes sense to add an st.iframe command directly into the st namespace.

Why?

• Easier to discover.
• Let's us move out of the st.components.v1 API.
• st.components.v1.iframe has some weird settings and does not allow rendering PDFs

How?

No response

Additional Context

• Related automatic/dynamic height for iframe/html component #4659