Update Fyne to v2.4.0

This release modernizes the project quite a bit.

Better metadata and sandbox permissions

This release upgrades the Fyne version to 2.1.2 for a fix that now allows us to drop the sandbox permission for the local preferences folder. The example metadata has also been updated to display more information.

Support for showing notifications

This release adds support for showing notifications and also updates Fyne to 2.1.1.

An example release

This is an example release to use for the manifest in this repository.

An initial test release

Just a simple release to test the build. Nothing special.