Fix package dependency (#148)

* Have StandardTypes package depend on core, as it requires generated code before it can compile.

Author: zeroZshadow

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Internal
+
+- Fixed package dependencies.
+
 ## `0.2.0` - 2019-03-19
 
 ### Added

workers/unity/Packages/com.improbable.gdk.standardtypes/package.json

@@ -6,5 +6,6 @@
     "author": "Improbable Worlds Ltd",
     "description": "SpatialOS GDK Standard Types Module. Made by Improbable.",
     "dependencies": {
+        "com.improbable.gdk.core": "0.2.0"
     }
 }