Recommended

Adds helper systems to make it easier to contribute to packer projects and use enforce robustness.Full details below.

• Added put_precommit_hook to add a pre-commit git hook that
  ebsure JavaScript files have been minified on commit.
• Added engine_adapt to easily change engine dependending
  on the current project's engine.
• Added engine_which to retrieve which engine the current
  project is using.
• Added put_rprofile_adapt to add engine_adapt to the
  .Rprofile.
• Added checks to run basic checks on packer projects.
• Added use_loader_svelte.
• Added add_plugin_workbox for progressive web applications.
• Added add_plugin_jsdoc for generating documentation from
  JavaScript code à la roxygen2, as well as add_jsdoc_tutorial
  to add vignettes-like documents.
• Added scaffold_leprechaun to scaffold an application for
  a leprechaun project.
• Remove use_loader_eslint, previously deprecated, see
  add_plugin_eslint.