[No QA] [TS migration] Migrate 'StartupTimer' lib to TypeScript

src/libs/StartupTimer/index.native.ts

@@ -0,0 +1,13 @@
+import {NativeModules} from 'react-native';
+import StartupTimer from './types';
+
+/**
+ * Stop the startup trace for the app.
+ */
+const startupTimer: StartupTimer = {
+    stop: () => {
+        NativeModules.StartupTimer.stop();
+    },
+};
+
+export default startupTimer;

src/libs/StartupTimer/index.ts

@@ -0,0 +1,11 @@
+/**
+ * Web noop as there is no "startup" to time from the native layer.
+ */
+
+import StartupTimer from './types';
+
+const startupTimer: StartupTimer = {
+    stop: () => {},
+};
+
+export default startupTimer;

src/libs/StartupTimer/types.ts

@@ -0,0 +1,5 @@
+type StartupTimer = {
+    stop: () => void;
+};
+
+export default StartupTimer;