Add definition of wxFont to header.

Fix:
../src/slic3r/Utils/EmbossStyleManager.hpp:219:42:   required from here
/opt/rh/devtoolset-10/root/usr/include/c++/10/type_traits:1239:4: error: invalid use of incomplete type 'class wxFont'

src/slic3r/Utils/EmbossStyleManager.cpp

@@ -1,5 +1,4 @@
 #include "EmbossStyleManager.hpp"
-#include <wx/font.h>
 #include <GL/glew.h> // Imgui texture
 #include <imgui/imgui_internal.h> // ImTextCharFromUtf8
 #include "WxFontUtils.hpp"

src/slic3r/Utils/EmbossStyleManager.hpp

@@ -5,12 +5,11 @@
 #include <optional>
 #include <string>
 #include <imgui/imgui.h>
+#include <wx/font.h>
 #include <GL/glew.h>
 #include <libslic3r/Emboss.hpp>
 #include <libslic3r/AppConfig.hpp>
 
-class wxFont; 
-
 namespace Slic3r::GUI::Emboss {
 /// <summary>
 /// Manage Emboss text styles