build: set up tsdown for dual build (#147)

* build: set up tsdown for dual build

* chore: use node12 target

Co-authored-by: Superchupu <53496941+SuperchupuDev@users.noreply.github.com>

* chore: update latest tsdown

* fix: use npm as expected

* chore: use fixedExtension

Co-Authored-By: sxzz <sxzz@sxzz.moe>

* chore: remove publint

* Update package.json

Co-authored-by: Superchupu <53496941+SuperchupuDev@users.noreply.github.com>

---------

Co-authored-by: Superchupu <53496941+SuperchupuDev@users.noreply.github.com>
Co-authored-by: sxzz <sxzz@sxzz.moe>

Author: 3 people