Add VITE_BASE_PATH to .env.sample

Author: ryangoree

apps/hyperdrive-trading/.env.sample

@@ -60,4 +60,8 @@ VITE_ADDRESS_SCREEN_URL=
 
 # Debugging options
 # logs why a component re-rendered, keep this off in production!
-VITE_ENABLE_WHY_DID_YOU_RENDER=
+VITE_ENABLE_WHY_DID_YOU_RENDER=
+
+# If deploying to a subdirectory
+# Typically added as a repo secret or in the deployment environment
+VITE_BASE_PATH=/