add 7z to PATH

Installation.md

@@ -5,6 +5,17 @@ You can find the latest binary at the following link:
 - flatpak : https://flathub.org/apps/details/io.github.ciromattia.kcc
 - Docker: https://github.com/ciromattia/kcc/pkgs/container/kcc
 
+#### 7-Zip
+
+##### Windows
+
+First install 7z from https://www.7-zip.org/
+
+Then add 7z to PATH via `setx path "%path%;C:\Program Files\7-Zip"`
+##### Mac
+
+TODO
+
 #### MacOS installation    
 ##### x86_64 version
 see: KindleComicConverter_osx_*.dmg in **https://github.com/ciromattia/kcc/releases**