Change the Thumbnail when sharing dashboards

[royendo]

Is your feature request related to a problem? Please describe.
Sharing dashboards internally, every time the Rill Data dashboard is shown, any way to customize this?

Describe the solution you'd like
Either 1) shorter graph/dashboard icon or 2) something so it's more apparent what's in the link. Like a low res version of a rill dashboard

Additional context
FR from Angel:
https://rilldata.slack.com/archives/C07KSF2DPPV/p1725657045034699

[mindspank]

@ericpgreen2 any chance we could squeeze in the change of our unfurl preview images in this upcoming sprint?

[ericpgreen2]

@ericpgreen2 any chance we could squeeze in the change of our unfurl preview images in this upcoming sprint?

I'll defer to @jkhwu :). This actually doesn't require any Application changes. Once we have the new image, we just need to overwrite rill-admin.png referenced here:

<meta
  property="og:image"
  content="https://storage.googleapis.com/prod-cdn.rilldata.com/images/rill-admin.png"
/>