scancode-next: Improve documentation, review documentation issues and pull requests #324

Triage open documentation issues and PRs, fix outdated or missing sections reported by users. This covers architecture, how major modules work (scan pipeline, license and copyright detection, code matching, package detection, plugins, output formats, API) and improved getting started based on user feedback to guide users across the whole stack.

See: https://github.com/aboutcode-org/scancode-toolkit/issues?q=is%3Aissue+state%3Aopen+label%3Adocumentation