I have created two libraries, one to check for updates (Linux and Windows) and one library to update AppImage (Linux)
This program uses binaries from these projects.
You can find the projects here.

libcheckforupdates
libzsyncupdateappimage

The "portable" versions for Windows
are not installed.
Delete the folder with the program and
the program is deleted.

"AppImage" for Linux can update itself.

All versions can check for updates.

Downloads for
Linux

AppImage for Linux 64 bit 33.0 MB
MD5: 15f2d30ee5ecb6862d5ff28268c2bd76

Make the downloaded file executable.
chmod +x fileName

Downloads for
Windows

Portable for Windows 64 bit 24.3 MB
MD5: f22dd623202fd376176df3ac43da95ca