book: add NIP21 JavaScript examples

[RydalWater]

Description

• Updated index.js
• Added nip21.js
• Updated nip21.md

Notes to the reviewers

Wasn’t able to adde the full URI examples for note and npub, figured it was related to the JS bindings not having toNostrUri() method exposed currently. If you’re able to add this let me know and I’ll update the examples.

Similarly, consider adding fromNostrUri() to the the Coordinate class and I’ll tweak the current Bech32 example so that it show how to decode the URI.

Finally, I noticed the NIP21 with parse() method wasn’t available for the js bindings, as with python. Was this intentional or is it a limitation of the js binding themselves?

Checklist

• I followed the contribution guidelines
• I ran just precommit or just check before committing
• I updated the CHANGELOG (if applicable)

[yukibtc]

Thanks, I'll add them. A thing that we can do for the next times (I'm going to do the same right now) is to add the example also for missing stuff but commented with a prefix, like:

// UNCOMMENT_ON_RELEASE: let pk_uri = keys.publicKey.toNostrUri();
// UNCOMMENT_ON_RELEASE: console.log(` Public key (URI): ${pk_uri}`);

[yukibtc]

Regarding the NIP21 parse: unfortunately I can't expose enums with fields in variants in JavaScript

[RydalWater]

Regarding the NIP21 parse: unfortunately I can't expose enums with fields in variants in JavaScript

Figured this was the case. No worries, cheers