Add terms to public_bookcase: 'book exchange shelf', 'book swap' (#1354)

Author: danieldegroot2

data/presets/amenity/public_bookcase.json

@@ -32,12 +32,14 @@
         "area"
     ],
     "terms": [
-        "book sharing",
         "bookcrossing",
+        "book exchange shelf",
+        "book sharing",
+        "book swap",
         "library",
+        "little free library",
         "share a book",
-        "sharing books",
-        "little free library"
+        "sharing books"
     ],
     "tags": {
         "amenity": "public_bookcase"