[FEATURE] Flag for changing update notice on packaged editions

[alfonsojon]

Is your feature request related to a problem? Please describe.
When using a packaged version of the launcher (currently Flatpak) the update does not work properly

Describe the solution you'd like
It would be useful to add a flag to launch the launcher which will change the Update available behavior. This will be useful if Betacraft is ever packaged by package maintainers for Linux distributions such as through Flathub or the Snap Store. Currently, the update mechanism does not work for copies installed by Flatpak or Snap, nor should it - it is the responsibility of the packager to update the build. By adding a flag to disable the manual download, we can instead notify the end user to contact their package maintainer to update the launcher to the latest copy or to download the .jar from the Betacraft site.

As an example:

Update available
ℹ️ There is a new version of the launcher available. Contact your packager for details.
[ Manual Download ] [Ignore] [Continue]

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.