Add an auto-updater

[tareh7z]

It would be nice to add an auto-updater to TaskMon, similar to the one in Paperback. That way, users could easily get the latest version without having to manually download and install each update.

[trypsynth]

Not sure on this one tbh. I'm not opposed to the feature, but I think I'd have it not notify you on startup, and I am worried about what this could do to binary size. Will consider it and thanks of openthe this!