(appimage/) add manual appimage

the existing one is broken, and i think it might be tauri's fault.

appimage/drop-oss-app.d/.DirIcon

@@ -0,0 +1 @@
+drop-oss-app.png

appimage/drop-oss-app.d/AppRun

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+program="drop-oss-app"
+
+# point to libraries and run
+LD_LIBRARY_PATH=$APPDIR/usr/lib:/usr/local/lib:/usr/lib $APPDIR/usr/bin/$program $@
+
+# vim:ft=sh

appimage/drop-oss-app.d/drop-oss-app.desktop

@@ -0,0 +1,7 @@
+[Desktop Entry]
+Name=drop-oss-app
+Comment=The client application for the open-source, self-hosted game distribution platform Drop
+Exec=AppRun
+Icon=drop-oss-app
+Type=Application
+Categories=Game;Network