feat(JS): add JS libraries from macchina.io

Origin

JS is a macchina.io platform library. As decided by the POCO team, it moves into POCO for release 2.0. The appinf and aleph-us lineages are consolidated, and the code is licensed under the POCO license (BSL-1.0).

Scope

• JS/Core, JS/Bridge, JS/Data, JS/Net, JS/File and related wrapper libraries
• JavaScript engine: decide between the bundled V8 (appinf lineage) and Node.js/libnode (aleph-us lineage, V8 12.x); the engine choice determines the build integration
• Testsuites and samples

Tasks

• Import sources (library, testsuite, samples, documentation), preserving history where practical
• Adapt namespaces, include paths and POCO_* macros to POCO conventions; ASCII-only sources
• GNU make build (Makefile, components, build/config)
• CMake build (CMakeLists.txt, cmake/Poco*Config.cmake, ENABLE_JS option)
• Testsuite runs in CI (Linux, macOS, Windows)
• PocoDoc documentation, doc/ overview page
• CHANGELOG / release notes entry for 2.0
• Reconcile divergence between the appinf and aleph-us lineages

Dependencies

Foundation, JSON, Net, Data, Util; V8 or libnode.