arrange operations into folders in line with grouping from the specification and start creating a context to mutate through operations.

src/UglyToad.Pdf/Graphics/Operations/TextState/SetFontSize.cs

@@ -0,0 +1,26 @@
+namespace UglyToad.Pdf.Graphics.Operations.TextState
+{
+    using Cos;
+
+    internal class SetFontSize : IGraphicsStateOperation
+    {
+        public const string Symbol = "Tf";
+
+        public string Operator => Symbol;
+
+        public CosName Font { get; }
+
+        public decimal Size { get; }
+
+        public SetFontSize(CosName font, decimal size)
+        {
+            Font = font;
+            Size = size;
+        }
+
+        public override string ToString()
+        {
+            return $"{Font} {Size} {Symbol}";
+        }
+    }
+}