Please provide Appstream data and desktop launcher

[TomaszGasior]

.desktop file is needed to show icon in desktop environment, to make it possible to launch app from GUI. Appstream data is useful for software catalogs like Discover in KDE and GNOME Software.

Please take a look at specs:

• https://www.freedesktop.org/software/appstream/docs/
• https://specifications.freedesktop.org/desktop-entry-spec/latest/

I prepared basic desktop activator and appstream data for Flatpak package. https://github.com/TomaszGasior/flathub/tree/de.blobbyvolley.BlobbyVolley2