adding in PlainTokenizer to unpooled SB changes

src/UglyToad.PdfPig.Tokenization/PlainTokenizer.cs

@@ -1,11 +1,12 @@
 namespace UglyToad.PdfPig.Tokenization
 {
     using Core;
+    using System.Text;
     using Tokens;
 
     internal class PlainTokenizer : ITokenizer
     {
-        private static readonly StringBuilderPool StringBuilderPool = new StringBuilderPool(10);
+        private readonly StringBuilder stringBuilder = new();
 
         public bool ReadsNextByte { get; } = true;
 
@@ -18,7 +19,7 @@
                 return false;
             }
 
-            var builder = StringBuilderPool.Borrow();
+            var builder = stringBuilder;
             builder.Append((char)currentByte);
             while (inputBytes.MoveNext())
             {
@@ -39,7 +40,7 @@
             }
 
             var text = builder.ToString();
-            StringBuilderPool.Return(builder);
+            builder.Clear();
 
             switch (text)
             {

src/UglyToad.PdfPig.Tokenization/Scanner/CoreTokenScanner.cs

@@ -15,10 +15,10 @@
         private static readonly DictionaryTokenizer DictionaryTokenizer = new DictionaryTokenizer();
         private static readonly HexTokenizer HexTokenizer = new HexTokenizer();
         private static readonly NameTokenizer NameTokenizer = new NameTokenizer();
-        private static readonly PlainTokenizer PlainTokenizer = new PlainTokenizer();
 
         // NOTE: these are not thread safe so should not be static. Each instance includes a
         // StringBuilder it re-uses.
+        private readonly PlainTokenizer PlainTokenizer = new PlainTokenizer();
         private readonly NumericTokenizer NumericTokenizer = new NumericTokenizer();
         private readonly StringTokenizer StringTokenizer = new StringTokenizer();