Improve the documentation: explain how to watch files from the command line

Created by: AeonFr

Hello. I just did a fresh install on node and gulp.

I'm following the documentation at https://gulpjs.com/docs/en/getting-started/watching-files

The code samples explain how to set up a gulpfile to watch files. Yet, after trying to run gulp, gulp --watch or any other command using the sample gulpfile, I encounter an error:

[15:54:06] Task never defined: default

It would be nice if the site explained how to use the code sample it provides. For newbies like me.

A google search points out on that documentation article as first result, and other tutorials seem to be old, that's why I find this necessary.

For now I will continue using the gulp-watch npm package.

Thanks.