Feature request

I'd like to propose a feature where the validation app automatically compares it's version number against the latest released version of the app and logs a notice if there is a newer version available. The old-school transitfeed validator had a similar feature and I think it was helpful for encouraging folks to run the latest version of the application. In light of the new packaged app, it's beneficial to get something like this implemented sooner rather than later, in order to have it in place for new users installing the application.

Is your feature request related to a problem? Please describe.
Folks tend to let software get stale and out-of-date if we don't prod them to upgrade.

Proposed solution
Similar to the transitfeed implementation, the app would read the content of a dedicate page on the gtfs-validator GitHub site, which would contain the latest released version number of the app. During validation, the app would read that page to find the latest version number and compare against its own internal version number in MANIFEST.MF. If the app is out-of-date, a notice would be added to the validation report.

Additional context
I am happy to do the implementation work on this if there is consensus that it is a worthwhile feature.