Update metainfo.xml for release 7.9.0

Added new release version 7.9.0 with detailed features and improvements.

Modify source URL and checksum fields in PKGBUILD

Updated source URL and checksum placeholders in PKGBUILD.

Update io.github.Loganavter.Improve-ImgSLI.metainfo.xml

Mega update after refactoring

Update io.github.Loganavter.Improve-ImgSLI.metainfo.xml

Update improve-imgsli-launcher.sh

Update improve-imgsli-launcher.sh

Hot fix for flatpak

Update readme.md

Update readme.md