packages: add lutris

- download the .deb package from OpenBuildService and add it to config/packages.chroot/
- the package will be auto-upgraded when it is added to Debian repositories https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=754129
- we could also add the OpenBuildServie repository to sources.list but that would mean trusting a third-party repository, which we might not want
- in the future we should verify package integrity/authenticity with GPG signatures (#56)

Makefile.extra

@@ -32,7 +32,9 @@ download_extra:
 	mv cache/downloads/user.js-0.1/systemwide_user.js config/includes.chroot/etc/firefox-esr/firefox-esr.js
 	# https://github.com/EionRobb/pidgin-opensteamworks/
 	-mkdir -p config/packages.chroot
-	$(WGET) https://gitlab.com/nodiscc/pidgin-opensteamworks/-/jobs/471942010/artifacts/raw/pidgin-opensteamworks_1.7-buster0-1_amd64.deb -O config/packages.chroot/pidgin-opensteamworks_1.7-buster0-1_amd64.deb
+	$(WGET) https://gitlab.com/nodiscc/pidgin-opensteamworks/-/jobs/471942010/artifacts/raw/pidgin-opensteamworks_1.7-buster0-1_amd64.deb
+	# https://lutris.net/downloads/ - https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=754129
+	$(WGET) https://download.opensuse.org/repositories/home:/strycore/Debian_10/amd64/lutris_0.5.7.1_amd64.deb
 	# https://addons.mozilla.org/en-US/firefox/addon/keepassxc-browser/
 	# https://addons.mozilla.org/en-US/firefox/addon/cookie-autodelete/
 	mkdir -p config/includes.chroot/usr/lib/mozilla/extensions/{ec8030f7-c20a-464f-9b0e-13a3a9e97384}