Add config.json file to numbers-floating-point exercise (exercism#766)

Author: ErikSchierboom

exercises/concept/numbers-floating-point/.meta/config.json

@@ -0,0 +1,8 @@
+{
+  "contributors": [
+    {
+      "github_username": "ErikSchierboom",
+      "exercism_username": "ErikSchierboom"
+    }
+  ]
+}