Documents UI version 2 - Webpack and sandbox installation

Additions and enhancements for documents UI version 2 documentation:

Essential - add a Webpack installation guide to getting started: https://terminusdb.com/docs/index/terminusx-db/how-to-guides/generate-document-user-interfaces/get-started-with-the-documents-user-interface
Optional - Documents UI with Common or Node JS (if possible)
Optional - enable Sandboxed code examples

terminusdb / terminusdb-docs