New specs for review

[github-actions]

find-specs has identified the following candidates as potential new specs to consider:

• https://tc39.es/proposal-arraybuffer-base64/ from tc39/proposal-arraybuffer-base64
• https://wicg.github.io/digital-identities/ from WICG/digital-identities
• https://wicg.github.io/discourse-archive/ from WICG/discourse-archive

Please review if they match the inclusion criteria. Those that don't and never will should be added to ignore.json, those that don't match yet but may in the future can be added to monitor-repo.json, and those that do match should be brought as a pull request on specs.json.

[dontcallmedom]

dup of #1203 (and pending #1204)