Fix: skypack build

[Gozala]

This change is based on #65 which fixes failing tests that were introduce in b34083f

This change just fixes export maps as per https://www.typescriptlang.org/docs/handbook/esm-node.html#packagejson-exports-imports-and-self-referencing which fixes build errors on skypack see https://cdn.skypack.dev/@noble/ed25519

/*
 * [Package Error] "@noble/ed25519@v1.6.0" could not be built. 
 *
 *   [1/5] Verifying package is valid…
 *   [2/5] Installing dependencies from npm…
 *   [3/5] Building package using esinstall…
 *   Running esinstall...
 *   Cannot find module '@noble/ed25519/index.d.ts'
 *
 * How to fix:
 *   - If you believe this to be an error in Skypack, file an issue here: https://github.com/skypackjs/skypack-cdn/issues
 *   - If you believe this to be an issue in the package, share this URL with the package authors to help them debug & fix.
 *   - Use https://skypack.dev/ to find a web-friendly alternative to find another package.
 */

console.warn("[Package Error] \"@noble/ed25519@v1.6.0\" could not be built. \n[1/5] Verifying package is valid…\n[2/5] Installing dependencies from npm…\n[3/5] Building package using esinstall…\nRunning esinstall...\nCannot find module '@noble/ed25519/index.d.ts'");
throw new Error("[Package Error] \"@noble/ed25519@v1.6.0\" could not be built. ");
export default null;

I believe skypack uses esbuild which in turns looks at export maps.