Implemented gif exportation and added some style (again)

GifResizer/Models/Format.cs

@@ -0,0 +1,18 @@
+namespace GifResizer.Models;
+
+public class Format
+{
+    public Format(int width, int height)
+    {
+        Width = width;
+        Height = height;
+        Checked = true;
+    }
+    
+    public int Width { get; private set; }
+    public int Height { get; private set; }
+    public bool Checked { get; set; }
+    
+    public override string ToString() => $"{Width}x{Height}";
+    
+}