Add new POPUPVINYL holdings location

How this addresses that need:
* Update holdings location crosswalk to handle new POPUPVINYL
location

Relevant ticket(s):
* https://mitlibraries.atlassian.net/browse/TIMX-400

Author: ghukill

config/holdings_location_crosswalk.json

@@ -14,6 +14,7 @@
     "LSA": "Library Storage Annex",
     "NET": "Internet Resource",
     "MUS": "Lewis Music Library",
+    "POPUPVINYL": "Pop-Up Vinyl Collection",
     "PHY": "Physics Department Reading Room",
     "RTC": "Rotch Library",
     "RVC": "Rotch Visual Collections",