schema: accommodate imprecise dates in the date field, supporting YYYY and YYYY-MM as well (#260)

Author: avivace

schemas/game-schema-d4.json

@@ -78,9 +78,17 @@
             "format": "uri"
         },
         "date": {
-            "type": "string",
-            "format": "date",
-            "description": "The date the entry was first released"
+            "anyOf": [
+                {
+                    "type": "string",
+                    "pattern": "^\\d{4}(-(0?[1-9]|1[0-2])(-(0?[1-9]|[12][0-9]|3[01]))?)?$"
+                },
+                {
+                    "type": "string",
+                    "format": "date"
+                }
+            ],
+            "description": "The date the entry was first released, expressed in ISO8601 format. To accommodate imprecise dates, the formats YYYY-MM (year and month) and YYYY (year only) are also supported"
         },
         "tags": {
             "type": "array",