Add valid time with leap second including offset

Author: kylef

tests/draft2019-09/optional/format/time.json

@@ -13,6 +13,11 @@
                 "data": "23:59:60Z",
                 "valid": true
             },
+            {
+                "description": "a valid time string with leap second with offset",
+                "data": "15:59:60-08:00",
+                "valid": true
+            },
             {
                 "description": "a valid time string with second fraction",
                 "data": "08:30:06.283185Z",

tests/draft2020-12/optional/format/time.json

@@ -13,6 +13,11 @@
                 "data": "23:59:60Z",
                 "valid": true
             },
+            {
+                "description": "a valid time string with leap second with offset",
+                "data": "15:59:60-08:00",
+                "valid": true
+            },
             {
                 "description": "a valid time string with second fraction",
                 "data": "08:30:06.283185Z",

tests/draft7/optional/format/time.json

@@ -13,6 +13,11 @@
                 "data": "23:59:60Z",
                 "valid": true
             },
+            {
+                "description": "a valid time string with leap second with offset",
+                "data": "15:59:60-08:00",
+                "valid": true
+            },
             {
                 "description": "a valid time string with second fraction",
                 "data": "08:30:06.283185Z",