LibGUI: Enable the use of font properties through GML

You can now specify the font, font_size, font_weight
and font_type (fixed_width/normal) through GML

Userland/Libraries/LibGfx/FontDatabase.h

@@ -34,6 +34,21 @@
 
 namespace Gfx {
 
+namespace FontWeight {
+enum {
+    Thin = 100,
+    ExtraLight = 200,
+    Light = 300,
+    Regular = 400,
+    Medium = 500,
+    SemiBold = 600,
+    Bold = 700,
+    ExtraBold = 800,
+    Black = 900,
+    ExtraBlack = 950
+};
+}
+
 class FontDatabase {
 public:
     static FontDatabase& the();