feat(gui): add freetype rasterizer backend

src/gui_config.zig

@@ -1,7 +1,14 @@
-fontface: []const u8 = "Cascadia Code",
+fontface: []const u8 = "IosevkaTerm Nerd Font Mono",
 fontsize: u8 = 14,
+fontweight: u8 = 0,
+fontbackend: RasterizerBackend = .freetype,
 
 initial_window_x: u16 = 1087,
 initial_window_y: u16 = 1014,
 
 include_files: []const u8 = "",
+
+pub const RasterizerBackend = enum {
+    truetype,
+    freetype,
+};