[SDK-563] Bump Web SDK version to v2.3.1

[joaodordio]

📝 Summary

Bump the Web SDK package version from 2.3.0 to 2.3.1 for the next release.

🎟️ Jira Ticket: SDK-563

📖 Description

Version bump for release. Updates version in package.json from 2.3.0 to 2.3.1 on the release/v2.3.1 branch, cut from main. Also promotes the Unreleased CHANGELOG entry for SDK-563 under ## [2.3.1]. No source or behavior changes beyond what's already on main.

🧪 How to test?

• Confirm package.json reads "version": "2.3.1".
• Confirm CHANGELOG.md has ## [2.3.1] with the preferUserId / tryUser fix, and an empty ## [Unreleased] section.
• CI (typecheck + jest) passes.

🧾 Changelog

CHANGELOG.md updated: Unreleased section moved under 2.3.1.

📹 Loom recording if applicable

N/A

🐞 Github Issues solved

N/A

📚 Docs PR if applicable

Follow-up: release notes for Web 2.3.1 in iterable-docs if needed (2.3.0 docs already covered the earlier preferUserId work).

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.43%. Comparing base (ad91607) to head (fa302a5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #583   +/-   ##
=======================================
  Coverage   74.43%   74.43%           
=======================================
  Files          57       57           
  Lines        2742     2742           
  Branches      820      821    +1     
=======================================
  Hits         2041     2041           
  Misses        660      660           
  Partials       41       41           

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[jena-chakour]

LGTM