* feat: use `package_json` to manage `package.json`

* fix: add `require` back maybe?

* fix: use `read` and leave the package manager to `package_json` (as it now has an env variable)

* fix: update `PackageJson` call

* fix: don't check yarn anymore

* fix: use bang method & exit early on error

* fix: use `package_json` rather than `yarn bin` to exec webpack

* fix: replace `check_yarn` with `check_manager` task

* fix: show general package manager name & version in info task

* refactor: make runners use of `PackageJson` opt-in

* refactor: make rake tasks use of `PackageJson` opt-in

* refactor: restore `check_yarn` rake task, based on opt-in flag for `PackageJson`

* refactor: make use of `PackageJson` in template tasks opt-in

* fix: only use `npm` for getting node package version if not using `package_json` gem

* fix: preserve old load paths when requiring `package-json` gem

It seems that requires which happen after this are mucked up due to the load paths having been
changed - this really only seems to impact RSpec which requires the diff library lazily

* fix: read `package.json` within app path

* fix: address minor bugs discovered from adding specs for when `package_json` is enabled

* test: update generator specs

* ci: run tests both with and without using `package_json` gem to ensure everything is valid

* docs: include a section about `SHAKAPACKER_USE_PACKAGE_JSON_GEM`

* fix: properly set babel preset for react

* feat: support bun

* feat: properly include `package_json` as a dependency

* ci: run generator specs with and without `package_json` gem in parallel

* docs: add changelog entry