Add missing screenshot of editor widget

[GeraldJansen]

Page https://github.com/projecthamster/hamster/wiki has some screenshots but one is missing. This PR adds a screenshot of the editor window accessible from the wiki as a blob.

[github-actions[bot]]

Automatically generated build artifacts for commit 6de7a4256f25d03d3a366cfc389f54e2a2e7a98a (note: these links will expire after some time):

• Flatpak application: :arrow_double_down: Download

To test this PR, download and unzip the flatpak application above and then install with:

flatpak install Hamster.flatpak

[aquaherd]

Will merge this if no objections given.