JS native output from json (to npm_dist)

[jacogr]

Adds scripts/js/build_js.mjs that does the following -

1. create index.{js, cjs} versions from the ss58-registry.json input
2. adjusts the package.json file to allow for export maps
3. adds an explicit index.d.ts file for TypeScript consumers

This is executed via npm run build that creates the output in the npm_dist folder. At this point is is completely ready for publishing to the npm registry, so cd npm_dist && npm publish --access public will publish (assuming all the right credentials are found locally)

The reason for the JS outputs is that import or require from json is still well, up-in-the-air from a standards perspective. For instance under Node extra flags are now required to enable this.

In general having a full build setup via something else would probably be overkill, hence the small script that copies stuff and generates the JS output. Cannot beat no additional dependencies.

Additionally the PR also adds -

• a types.d.ts file in the root for TypeScript definitions for the registry structure
• an updated .gitignore to skip the npm_dist folder (alongside the changes in Version package.json from Cargo.toml (via script) #33)
• alignment for the package.json version from the current master status

With this available alongside #33 it can really be published to npm from CI.

[jacogr]

After this, it ends up looking like this in npm_dist/index.js -

export default [
	{
		prefix: 0,
		network: 'polkadot',
		displayName: 'Polkadot Relay Chain',
		symbols: [
			'DOT'
		],
		decimals: [
			10
		],
		standardAccount: '*25519',
		website: 'https://polkadot.network'
	},
	{
		prefix: 1,
...

[bkchr]

Needs to be updated