Support Screenshot

[buenaflor]

Mobile SDKs can capture screenshots and send envelope items with image/png content type. The overlay cannot process events with screenshots currently which leads to them not being displayed although they were ingested properly through the side car

[Shubhdeep12]

Hi @buenaflor please follow these steps - https://spotlightjs.com/contribute/development/
And provide a sample file to debug the issue. It will help the team to debug the issue.
Thanks

[BYK]

We now have a sample envelope with a screenshot in it: https://github.com/getsentry/spotlight/blob/main/packages/overlay/_fixtures/envelope_with_screenshot.bin

I think this can be done along with implementing attachments support.

[BYK]

FYI we fixed the processing error in #631 so constructing the image shouldn't be too hard at this point.

[BYK]

We may need to add msgpack decoding for these: https://msgpack.org/index.html