Add PdfDocument#findFont() for already added PdfFonts

DEVSIX-2068

Autoported commit.
Original commit hash: [40968cf74]

Author: pavel-alay

itext.tests/itext.kernel.tests/itext/kernel/pdf/PdfFontCacheTest.cs

@@ -72,7 +72,7 @@ public class PdfFontTest : ExtendedITextTest {
 
         internal const String creator = "iText 7";
 
-        internal const String pangramme = "Amazingly few discothegues provide jukeboxes" + "but it now while sayingly ABEFGHJKNOPQRSTUWYZ?";
+        internal const String pangramme = "Amazingly few discotheques provide jukeboxes " + "but it now while sayingly ABEFGHJKNOPQRSTUWYZ?";
 
         [NUnit.Framework.OneTimeSetUp]
         public static void BeforeClass() {