Load the version from FyneApp.toml instead of hard coding

[Jacalz]

Checklist

• I have searched the issue tracker for open issues that relate to the same feature, before opening a new one.
• This issue only relates to a single feature. I will open new issues for any other features.

Is your feature request related to a problem?

Right now the current release version is hard-coded into the binary and the link to the release just naively points to a GitHub tag with the same name. This works well for our released binaries but the link will either be pointing to an older tag or a tag that do not yet exist depending on when the version gets updated.

Describe the solution you'd like to see.

Update the about page to try to use the version from FyneApp.toml if that has been bundled. If not, then we need to consider the two options:

• Flatpak or Linux distributions that do not package using Fyne tooling: Show the correct version.
• Development versions should somehow indicate that they are development versions.

It might be problematic to make those two work. Let's try to see what we can do.