Add method to get JSON from a file without using file_get_contents()

[aristath]

This came up on a discussion about the use of file_get_contents() in WP Themes. Right now that function is banned and for good reason on w.org themes since it can be grossly abused and lead to malicious code.
However, recently it became a recommendation in ​https://github.com/WordPress/gutenberg/blob/9ce596cd568d30c76fd4a0257e2872da91d4966a/packages/dependency-extraction-webpack-plugin/README.md#wordpress

There was further discussion in the #core-editor slack channel - see ​https://wordpress.slack.com/archives/C02QB2JS7/p1558546491251400 for reference.

The suggestion was to add a new method/function to get what is required, without forcing plugin and theme authors to use file_get_contents(), and we could add any security checks required in that function.

[youknowriad]

I wonder if this should just be the default behavior of wp_register_script if you omit the "deps" argument. It could go check if there's a dependency file with the same name as the script and load it.

[aristath]

Interesting suggestion... And makes perfect sense. If we have a way to register script dependencies outside of wp_register_script, then omitting the deps argument should load the defaults