Handle incoming drag and drop on every surface of the app

[Meteor0id]

• I have searched open and closed issues for duplicates

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Bug Description

Actual Result:
As of now, I can drag and drop an image file on the compose field. and the iamge will be added as a preview to be send. Great.

Expected Result:
But I only found out about this on my third attempt to use drag and drop, because I first tried dropping in other places:

• If the app opened on the wrong chat, I should be able to drag and hover over an an other conversation in the conversation list on the left, and the app should switch to that conversation while I am still holding the image.
• If I drop the image on the conversation rather than the compose field, the app should still accept the image and show it as a preview

This issue also applies to the sticker creator, which was mentioned here:
https://community.signalusers.org/t/beta-feedback-for-the-upcoming-desktop-1-30-release/10644/62?u=meteor0id

Platform Info

Signal Version:
v 3.30.0-beta.3

Operating System:

Windows 10 64-bit 1903

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Exploder98]

Bump.