EAP TLS 1.3 Handshake Extensions

Hello Community, I am using EAP-TLS 1.3 and wan't to add an TLS Extension (not an X509 extension), to the handshake message (Certificate Request), in order to add the OID-Filters defined in TLS 1.3. Is this a configuration or a source code extension I need to do in Freeradius? Or is it purely in OpenSSL? Appreciate any help, Dincer