Add independent Rust engine, deterministic mod API and asset pipeline

examples/mods/aurora/scripts/cell.rhai

@@ -0,0 +1,11 @@
+fn on_pickup(event, state, random) {
+    let recovered = if state.contains("recovered") { state.recovered + 1 } else { 1 };
+    #{ commands: [#{ op: "credits", amount: 25 }], state: #{ recovered: recovered } }
+}
+
+// A selected repair cell can also be consumed with the special-action button.
+fn on_use(event, state, random) {
+    let used = if state.contains("used") { state.used + 1 } else { 1 };
+    state.used = used;
+    #{ commands: [#{ op: "objective", key: "aurora:repairs_used", value: used }], state: state }
+}