lib:*: Blessed gap-fillers and project-native modules

Modules that don't fit std:* (Rust std mirrors) or vnd:* (single vendored crates). Two kinds: gap-fillers (lib:base64) and project-native modules (lib:test, lib:json).

Qualifies when: well-defined purpose, stable surface, genuinely useful to most scripts.

Reference

• lib:base64 — Base64 encoding/decoding
• lib:json — JSON Object/Array handles, null sentinel
• lib:mime — MIME type detection and extension mapping
• lib:test — Luau test runner and assertions
• lib:vcr — Record-and-replay HTTP fixtures

See also

• The module system
• std:*
• vnd:*