Opening support for both Mac and Linux in downloader.sh

Closes issue NITDgpOS#21

BASH/downloader.sh

@@ -1,6 +1,14 @@
-index(){
+index() {
 	echo "$(echo $@ | grep -aob '"' | grep -oE '[0-9]+' | sed "${!#};d")"
 }
+
+os=$(uname)
+if [ "$os" = "Linux" -o "$os" = "FreeBSD" ]; then
+	openWith="xdg-open"
+elif [ "$os" = "Darwin" ]; then
+	openWith="open"
+fi
+
 a="$#"
 declare -i chaps=0,chape=0,t=0,c=0,end_loop=0,d1=0,d2=0
 #checking for existence of -t , --chap in argument
@@ -65,7 +73,7 @@ do
 	fi
 	rm index.html
 	declare -i i=1
-	while true  #an infinte while loop
+	while true  #an infinite while loop
 	do
 		echo "Downloading page $i of chapter $chap....."
 		wget -o log.txt -O $i.html -c www.mangareader.net/$manga/$chap/$i # Downloads the main webpage
@@ -96,6 +104,6 @@ do
 	path=$(pwd)
 	echo -e "Your downloaded file is in this path:\n" $path
 	cd ..
-	xdg-open chap$chapno.pdf
+	$openWith chap$chapno.pdf
 	rm -rf $chap
 done