cppeditor: add resource preview hover handler class

This adds a hover handler which will preview images
from within project resource.

Change-Id: I88bcb56a977e41ed4dc5bfe165e2c80d4396a21f
Reviewed-by: André Hartmann <aha_1980@gmx.de>
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/cppeditor/cppeditorplugin.cpp

@@ -38,6 +38,7 @@
 #include "cppquickfixes.h"
 #include "cppsnippetprovider.h"
 #include "cpptypehierarchy.h"
+#include "resourcepreviewhoverhandler.h"
 
 #include <coreplugin/editormanager/editormanager.h>
 
@@ -106,6 +107,7 @@ public:
 
         addHoverHandler(new CppHoverHandler);
         addHoverHandler(new ColorPreviewHoverHandler);
+        addHoverHandler(new ResourcePreviewHoverHandler);
     }
 };