* **espowerify:**
  * use multi-stage-sourcemap module to generate more accurate sourcemaps ([b1f939fa](https://github.com/twada/espowerify/commit/b1f939faa84be7f4fde82313b2257042b336d25c))
  * if upstream SourceMap is given, decode and offset it ([a1683475](https://github.com/twada/espowerify/commit/a1683475a588b0a5b0aee040f23dfb04ad902b11))