js: release bolt12-utils v0.1.2

[vincenzopalazzo]

Summary

• Bump bolt12-utils 0.1.1 -> 0.1.2 (js/package.json, js/package-lock.json).
• Add js/CHANGELOG.md (Keep a Changelog format).

This is a release-metadata PR for the payer-proof data-range fix that landed in #33. No code changes beyond the version bump and changelog.

Changelog (0.1.2)

Fixed:

• Payer proof reader excludes the payer-proof data range (1001..=999_999_999) from invoice merkle reconstruction, so an unknown TLV there is no longer mis-counted as an invoice leaf (which wrongly failed the proof_leaf_hashes count). A record is an invoice field only when type < 240 or type >= 1_000_000_000, mirroring rust-lightning's tlv_stream_iter.
• Reject unknown even TLVs in the data range per the BOLT "it's ok to be odd" rule; unknown odd types remain ignorable and stay committed by proof_signature.

Notes

• dist/ is gitignored; npm publish regenerates it via prepublishOnly. The actual npm publish will be done after this merges.
• No tag created here — leaving the v0.1.2 tag / npm publish to the release step.

Test plan

• npm run build clean
• npm test — 53 + 36 + 22 + 3 all pass
• npm pack --dry-run -> bolt12-utils@0.1.2, 52 files, 57.6 kB