add reference to Unity.Collections for burst compatible attribute

Author: redwyre

Runtime/StrangeLoopGames.NativeTime.Runtime.asmdef

@@ -1,6 +1,7 @@
 {
     "name": "NativeTime",
     "references": [
+        "Unity.Collections"
     ],
     "optionalUnityReferences": [],
     "includePlatforms": [

package.json

@@ -8,5 +8,9 @@
   "keywords": [
     "NativeTime"
   ],
-  "type": "library"
+  "type": "library",
+  "dependencies": {
+    "com.unity.collections": "0.1.0"
+  },
+  "resolutionStrategy": "highest"
 }