added functionality previously seen in PortUtil in html2pdf to TextUtil to accomodate autoporting ease RND-788

Author: michaeldemey

io/src/main/java/com/itextpdf/io/util/TextUtil.java

@@ -46,6 +46,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.io.font.otf.Glyph;
 import com.itextpdf.io.font.otf.GlyphLine;
 
+import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -248,4 +249,12 @@ public static boolean isNonPrintable(int c) {
     public static boolean isWhitespaceOrNonPrintable(int code) {
         return Character.isWhitespace(code) || isNonPrintable(code);
     }
+
+    public static boolean charsetIsSupported(String charsetName) {
+        try {
+            return Charset.isSupported(charsetName);
+        } catch (IllegalArgumentException e) {
+            return false;
+        }
+    }
 }