Add [SdfLib](https://github.com/UPC-ViRVIG/SdfLib) plugin to first-party SDFs.

The following dependencies are disabled with a cmake patch file.
- Enoki
- OpenMP
- Assimp
- FCPW

PiperOrigin-RevId: 565352386
Change-Id: Icff9de68408e0afa2032bb83b24491fc4e41d181

plugin/sdf/register.cc

@@ -17,6 +17,7 @@
 #include "gear.h"
 #include "nut.h"
 #include "torus.h"
+#include "sdflib.h"
 
 namespace mujoco::plugin::sdf {
 
@@ -26,6 +27,7 @@ mjPLUGIN_LIB_INIT {
   Gear::RegisterPlugin();
   Nut::RegisterPlugin();
   Torus::RegisterPlugin();
+  SdfLib::RegisterPlugin();
 }
 
 }  // namespace mujoco::plugin::sdf