Cdnget

---------------------------

* Fix to ignore alpha or beta versions when using `latest` keyword on jsDelivr or UNPKG.
* Support `author/name` style NPM package name on jsDelivr and UNPKG.
* Tweak help message.
* Tweak error messages
* (internal) Change UNPKG to use metadata from unpkg.com.
* (internal) Make source code refactored.
* (internal) Change testing library from `minitest` to `oktest`.

---------------------------

* Improve help message.
* Update `README.md`.

---------------------------

* Skip downloading '.DS_Store' files from unpkg.com (due to 403 Forbidden)

---------------------------

* Download performance improved.
* New CDN `unpkg` supported.
* Change `jsdelivr` CDN to use new jsdelivr API.
* Detect latest version of JS library automatically when `latest` keyword specified as version.
* Increase output information of JS library.
- license
- tags
- page url on CDN web site
- url of npm package (`*.tgz`)
* Add '--debug' option.

---------------------------

* Fix to work on Ruby 3.
* Fix to follow API specification changes of CDNJS.com.

---------------------------

* Change to read data from https://api.cdnjs.com/ .