Resolve "Implement ffi_ZDC"

https://gitlab.com/eic/escalate/g4e/-/blob/master/src/subdetectors/ffi_ZDC/ffi_ZDC.hh

Closes #30 (closed)

compact/display.xml

@@ -49,6 +49,7 @@
     <vis name="BeamPipeVis"    alpha="1"  r= "0.75" g="0.75" b="0.75" showDaughters="true" visible="true"/>
 
     <vis name="cb_SolenoidVis" alpha="0.4"  r= "0.1"  g="0.0"  b="0.1"  showDaughters="true" visible="true"/>
+    <vis name="ffi_ZDCVis"     alpha="0.1"  r= "0.1"  g="0.0"  b="1.0"  showDaughters="true" visible="true"/>
 
     <comment>
       Deprecated colors.