package/libgdiplus: add LIBGDIPLUS_CPE_ID_VENDOR

cpe:2.3:a:mono-project:libgdiplus is a valid CPE identifier for this
package:

  https://nvd.nist.gov/products/cpe/search/results?namingFormat=2.3&keyword=cpe%3A2.3%3Aa%3Amono-project%3Alibgdiplus

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/libgdiplus/libgdiplus.mk

@@ -9,6 +9,7 @@ LIBGDIPLUS_SITE = $(call github,mono,libgdiplus,$(LIBGDIPLUS_VERSION))
 
 LIBGDIPLUS_LICENSE = MIT
 LIBGDIPLUS_LICENSE_FILES = LICENSE
+LIBGDIPLUS_CPE_ID_VENDOR = mono-project
 
 LIBGDIPLUS_INSTALL_STAGING = YES