Add 'Check for updates' functionality
Since the IDE is now officially released (see #30 (closed)), there is currently no possibility for users to check whether a new version was released beside manually checking at either pseuCo.com or the releases page.
In order to enhance the user experience, the IDE should provide some Check for updates mechanism, which can be triggered manually but also automatically during startup.
While thinking about it, I decided the following to be the best and easiest solution:
Since all releases correspond to tags in the repository, the check can be realized by comparing tags against each other. To do so, all available tags are queried using the GitLab API (https://dgit.cs.uni-saarland.de/api/v4/projects/16/repository/tags) and compared to the tag name the official release is build on. This makes use of the fact that all release tags follow a simple, yet consistent, scheme: ^v\d+\.\d+(\.\d+)?$.
If a new version is available, there are two possibilities:
- The correspondent download link is presented to the user, such that he can easily pass it to his browser.
- The user is redirected to the IDE site of pseuCo.com, which then includes the download link to the newest version.