Add wxHtmlTag::GetParamAsString() convenience method.

This is more convenient to use than HasParam() + GetParam() and also slightly
more efficient as we search for the tag name only once.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74879 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/html/htmltag.h

@@ -101,6 +101,7 @@ public:
     static bool ParseAsColour(const wxString& str, wxColour *clr);
 
     // Convenience functions:
+    bool GetParamAsString(const wxString& par, wxString *str) const;
     bool GetParamAsColour(const wxString& par, wxColour *clr) const;
     bool GetParamAsInt(const wxString& par, int *clr) const;
     bool GetParamAsIntOrPercent(const wxString& param,