feat(build): prevent submodules bundling their local dependencies

[alienzhou]

When importing a submodule, esm.sh tries to bundle all its local dependencies. If a local module has its 'inner state', it may occur some errors.

---

For example, here's a pkgA

 pkgA
   |-- lib
   |    |-- acc.js
   |    +-- print.js
   +-- index.js

The source code in lib/acc.js is something like

// lib/acc.js
let idx = 0;
export const acc = () => ++idx;

The source code in lib/print.js is something like

// lib/print.js
import { acc } from './acc.js';
export const print = () => console.log(acc())

So after building the lib/print.js submodule, the lib/acc.js's source code will be included.

When a third party package (pkgB) importing pkgA,

// pkgB
import { acc } 'pkgA/lib/acc.js';
import { print } 'pkgA/lib/print.js'

It actually uses two pkgA/lib/acc.js modules -- an original submodule and a copy in pkgA/lib/print.js. The idx variable is not shared.

---

the relative issue #353

[ije]

LGTM! thanks