Keep Rest-API (for now) as core

Yes or no? Not quite sure. I'd expect it's better as a side exercise, but I had no good reason so I kept it for now, nearly to the end of the track.

Author: emcoding

config.json

@@ -210,6 +210,17 @@
         "parsing"
       ]
     },
+    {
+      "slug": "rest-api",
+      "uuid": "2abe6eed-c7e4-4ad7-91e3-778bc5176726",
+      "core": true,
+      "unlocked_by": null,
+      "difficulty": 8,
+      "topics": [
+        "parsing",
+        "strings"
+      ]
+    },
     {
       "slug": "book-store",
       "uuid": "4899b2ef-675f-4d14-b68a-1a457de91276",
@@ -1379,17 +1390,6 @@
         "strings"
       ]
     },
-    {
-      "slug": "rest-api",
-      "uuid": "2abe6eed-c7e4-4ad7-91e3-778bc5176726",
-      "core": true,
-      "unlocked_by": null,
-      "difficulty": 8,
-      "topics": [
-        "parsing",
-        "strings"
-      ]
-    },
     {
       "slug": "affine-cipher",
       "uuid": "02bf6783-fc74-47e9-854f-44d22eb1b6f8",