fix: use asynchronous file write during bootstrapping

Author: mariotacke

bootstrap.sh

@@ -8,7 +8,7 @@ for input_file in `find . -type f ! -name 'README.md' ! -name 'bootstrap.sh' ! -
 do
   if [ ! -d "${input_file}" ]; then
     echo "Rendering file: ${input_file}"
-    sed -E 's/__(([^_]|_[^_])*)__/${\1}/g' "${input_file}" | envsubst > "${input_file}"
+    sed -E 's/__(([^_]|_[^_])*)__/${\1}/g' "${input_file}" | envsubst | tee "${input_file}"
   fi
 done