Get multiline values as a list for INI files.

Multiline values are now obtained as lists when parsing INI files (this is
the case of e.g. setup.cfg).

src/docformatter/configuration.py

@@ -367,6 +367,6 @@ def _do_read_parser_configuration(self) -> None:
         ]:
             if _section in config.sections():
                 self.flargs_dct = {
-                    k: v if isinstance(v, list) else str(v)
+                    k: v.split() if len(v.split()) > 1 else str(v)
                     for k, v in config[_section].items()
                 }