Generate template for each language

Generate template code which doesn't alter the implementation details.

- [ ] JavaScript/Typescript
  - use [swc_ecmascript_codegen](https://docs.rs/swc_ecma_codegen/latest/swc_ecma_codegen)
  - wait for 👆 to be properly documented
  - or just look at [bench.rs](https://github.com/swc-project/swc/blob/master/ecmascript/codegen/benches/bench.rs)
