Similar to the _map added for group_list SiteSettings in
e62e93f83a, this commit adds
the same extension for simple and compact `list` type SiteSettings,
so developers do not have to do the `.to_s.split("|")` dance
themselves all the time.
For example:
```
SiteSetting.markdown_linkify_tlds
=> "com|net|org|io|onion|co|tv|ru|cn|us|uk|me|de|fr|fi|gov|ddd"
SiteSetting.markdown_linkify_tlds_map
=> ["com", "net", "org", "io", "onion", "co", "tv", "ru", "cn", "us", "uk", "me", "de", "fr", "fi", "gov"]
```
eea74e0e32