virtual_sdcard: register sd static path

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

klippy/extras/virtual_sdcard.py

@@ -35,6 +35,9 @@ class VirtualSD:
         self.gcode.register_command(
             "SDCARD_PRINT_FILE", self.cmd_SDCARD_PRINT_FILE,
             desc=self.cmd_SDCARD_PRINT_FILE_help)
+        # Register sd path
+        webhooks = printer.lookup_object('webhooks')
+        webhooks.register_static_path("sd_path", self.sdcard_dirname)
     def handle_shutdown(self):
         if self.work_timer is not None:
             self.must_pause_work = True