linking to appimg:// URLs from github

[DetachHead]

it looks like custom URL schemes don't work on github, so i made this redirect site. for example:

https://detachhead.codeberg.page/urlwrapper/?url=appimg://install?url=https://github.com/kem-a/AppManager/releases/download/v3.8.0/AppManager-3.8.0-anylinux-x86_64.AppImage

i used it to add an "Install with AppManager" link to my project's readme.

[kem-a]

URL handler was introduced to work with apphub. It's a WIP towards unified AppImage repository