Generate a default client lokinet.ini on startup if it doesn't exist

Thus when a user goes looking for it they'll find the (commented out)
default in the right place and can edit it.

(That right place is: ~/Library/Containers/com.loki-project.lokinet.network-extension/Data/lokinet.ini)

llarp/apple/context_wrapper.cpp

@@ -40,9 +40,9 @@ llarp_apple_init(
   {
     auto config_dir = fs::u8path(config_dir_);
     auto config = std::make_shared<llarp::Config>(config_dir);
-    std::optional<fs::path> config_path = config_dir / "lokinet.ini";
-    if (!fs::exists(*config_path))
-      config_path.reset();
+    fs::path config_path = config_dir / "lokinet.ini";
+    if (!fs::exists(config_path))
+      llarp::ensureConfig(config_dir, config_path, /*overwrite=*/ false, /*router=*/ false);
     config->Load(config_path);
 
     // If no range is specified then go look for a free one, set that in the config, and then return