LibDraw: Put all classes in the Gfx namespace

I started adding things to a Draw namespace, but it somehow felt really
wrong seeing Draw::Rect and Draw::Bitmap, etc. So instead, let's rename
the library to LibGfx. :^)

Libraries/LibDraw/TextAlignment.h

@@ -26,6 +26,8 @@
 
 #pragma once
 
+namespace Gfx {
+
 enum class TextAlignment {
     TopLeft,
     CenterLeft,
@@ -44,3 +46,5 @@ inline bool is_right_text_alignment(TextAlignment alignment)
         return false;
     }
 }
+
+}