docs: change README with some rephrasing

README.md

@@ -18,9 +18,9 @@ There are many [Npm](https://www.npmjs.com/) packages that provide all or any of
 
 [This package](https://www.npmjs.com/package/@atao60/fse-cli) just provides many of them from a unique [CLI](https://en.wikipedia.org/wiki/Command-line_interface), without any pretention to be any kind of [shell](https://en.wikipedia.org/wiki/Shell_(computing)).
 
-It is based on the API [Node.js: fs-extra](https://github.com/jprichardson/node-fs-extra). 
+It is based on the `API` [Node.js: fs-extra](https://github.com/jprichardson/node-fs-extra). 
 
-> [@atao60/fse-cli](https://www.npmjs.com/package/@atao60/fse-cli) is not a library and should not be used as such. [Node.js: fs-extra](https://www.npmjs.com/package/fs-extra) is there for that. 
+> If an `API` is needed, use [Node.js: fs-extra](https://github.com/jprichardson/node-fs-extra), **not** [@atao60/fse-cli](https://www.npmjs.com/package/@atao60/fse-cli). If only because the latter uses `npm-shrinkwrap.json`, not `package-lock.json`, see [shrinkwrap.json - A publishable lockfile](https://docs.npmjs.com/cli/v6/configuring-npm/shrinkwrap-json).
 
 
 The [available CLI commands](#-commands) are fully functional and tested. However it's still a work in progress: