Make HTML message box close on escape key.

Fixes: https://gitlab.com/kicad/code/kicad/-/issues/6110

common/html_messagebox.cpp

@@ -127,3 +127,16 @@ void HTML_MESSAGE_BOX::ShowModeless()
 
     Show( true );
 }
+
+
+void HTML_MESSAGE_BOX::OnCharHook( wxKeyEvent& aEvent )
+{
+    // shift-return (Mac default) or Ctrl-Return (GTK) for OK
+    if( aEvent.GetKeyCode() == WXK_ESCAPE )
+    {
+        wxPostEvent( this, wxCommandEvent( wxEVT_COMMAND_BUTTON_CLICKED, wxID_OK ) );
+        return;
+    }
+
+    aEvent.Skip();
+}

include/dialog_shim.h

@@ -94,7 +94,8 @@ class DIALOG_SHIM : public wxDialog, public KIWAY_HOLDER
      */
     void OnButton( wxCommandEvent& aEvent );
 
-    void OnCharHook( wxKeyEvent& aEvt );
+protected:
+    virtual void OnCharHook( wxKeyEvent& aEvt );
 
 public:
 

include/html_messagebox.h

@@ -38,6 +38,8 @@ protected:
     // Handlers for HTML_MESSAGE_BOX_BASE events.
     void OnOKButtonClick( wxCommandEvent& event ) override;
 
+    virtual void OnCharHook( wxKeyEvent& aEvt ) override;
+
 public:
     HTML_MESSAGE_BOX( wxWindow* aParent, const wxString& aTitle = wxEmptyString,
                       const wxPoint& aPosition = wxDefaultPosition,