Add {set_exports} script for {ergo-lib-wasm}

[mkermani144]

When {wasm-pack} is run with browser target, it generates a {package.json} in which there is a {module} field, but no {main}, {type} or {exports} field is present. This causes some of the modern tools which run in Node be unable to use the package (Vitest is an example).

Although it may seem irrational to use the browser package in Node, but it makes sense when we want to write tests. Many test tools such as Jest and Vitest run in Node.

Add a {set_exports} script to be run after {wasm-pack}, updating the generated {package.json} as follows:

• Add an {exports} field to enable new Node entry resolution feature
• Add {"type": "module"} to indicate that this is an ESM module
• Remove {module}, as it's no longer needed

{wasm-pack} may fix the issue in the future or new module entry resolution mechanisms may be introduced in the future. Until then, this script will enable the use of the package without getting browser environment related issues when run in Node.

Related {wasm-pack} PR:
rustwasm/wasm-pack#1061

Closes #632.

[coveralls]

Pull Request Test Coverage Report for Build 3171835444

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 17 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.03%) to 88.52%

---

Files with Coverage Reduction	New Missed Lines	%
ergo-p2p/src/peer_info.rs	1	68.42%
ergo-lib/src/wallet/tx_builder.rs	2	90.26%
ergotree-interpreter/src/eval/sheader.rs	2	97.58%
ergo-p2p/src/peer_spec.rs	6	82.61%
ergotree-ir/src/serialization/types.rs	6	83.74%

Totals
Change from base Build 3013854837:	-0.03%
Covered Lines:	15800
Relevant Lines:	17849

---

💛 - Coveralls

[greenhat]

Thank you! Any chance these changes brake anyone's browser workflow?

[mkermani144]

I'm not sure, as it depends on the package resolution of build tool used. If there is a build tool which doesn't support exports field, this becomes a breaking change. But as far as I know, the exports field is supported in the well known build tools and we shouldn't count this as a breaking change.
In addition, if someone uses old versions of Node (~v12 or older, I think), this should be counted as breaking change, too.

[greenhat]

Looking great! Thank you!