Change lookback option to -B to match dwarfs

appdwarf

@@ -9,7 +9,7 @@ usage(){
     echo "Usage: $(basename "$0") [option] [FILE/FOLDER/URL]"
     echo "  Compress a given AppDir (default)"
     echo "    -a,  --appimage     Convert a given AppImage to appdwarf" 
-    echo "    -b,  --lookback     Change dwarfs block lookback amount"
+    echo "    -B,  --lookback     Change dwarfs block lookback amount"
     echo "    -f,  --folder       Make image mount to a specified folder instead of running AppRun"
     echo "    -s,  --separate     Use old, separated header format"
     echo "    -u,  --url          Fetch AppImage from URL and convert to appdwarf"
@@ -61,7 +61,7 @@ do
             header_folder "$(realpath "$2")"
             shift 2
             ;;
-        --lookback | -b) 
+        --lookback | -B) 
             back=$2
             shift 2
             ;;