Gmail add-on load an HTML page in the side panel

I'm wondering whether it's currently possible to build a Gmail add-on which would have a possibility to load some HTML page into it?

For example, let's assume. I have a resource someresource.com which I very frequently use when I read my emails basically working with Gmail. I would like to have an add-on on the side where I could click and the someresource.com will be loaded into the side panel. This would be very useful in this case. BTW there is such possibility in Outlook, meaning to create such extension.

From what I see right now in Gmail I could use

CardService.newOpenLink().setUrl('https://someresource.com').setOpenAs(CardService.OpenAs.OVERLAY)

Basically, open my resource in a new browser window. However, maybe I missed something and there is the possibility to load it into the side panel directly.

Thanks for any thoughts.

Solution

As mentioned in the comment, this doesn't seem possible.

Some of the functions in the CardService object support limited HTML formatting for bold, italic, underline, etc.