Support pdf files in file viewer (#259)

auto convert EOL

this fix it for me

fix layout

implement support for pdf files in file viewer

Co-authored-by: 6543 <6543@obermui.de>
Reviewed-on: https://gitea.com/gitnex/GitNex/pulls/259
Reviewed-by: 6543 <6543@noreply.gitea.io>

app/src/main/java/org/mian/gitnex/util/AppUtil.java

@@ -224,6 +224,14 @@ public class AppUtil {
 
     }
 
+    public Boolean pdfExtension(String ext) {
+
+        String[] extValues = new String[] {"pdf"};
+
+        return Arrays.asList(extValues).contains(ext);
+
+    }
+
     public Boolean imageExtension(String ext) {
 
         String[] extValues = new String[] {"jpg", "jpeg", "gif", "png", "ico"};