Example/docs for string_list_setting

Is there more documentation (preferably with examples) for using string_list_setting? I'm trying to pass defines to a cc_library rule, like this:

```
cc_library(
name = "...",
defines = ":nrf_defines",
)

string_list_setting(
name = "nrf_defines",
build_setting_default = [],
)
```

When I build this, cc_library rules spit out the error:

```
expected value of type 'list(string)' for attribute 'defines' in 'cc_library' rule, but got ":nrf_defines" (string)
```

This also makes sense, since the types are different, but I don't know how to proceed. How do I convert the string_list_setting into a list of strings when filling in the `defines` field of a cc_library?

Start with the string_list_setting and cc_library examples in the issue, then inspect the existing Bazel Skylib documentation for the relevant entry points. Done means the documentation explains how to use string_list_setting with cc_library defines and includes a working example of the expected value conversion.

Written by the indexing model from the issue text.