Add an example of center-justifying one column

Author: tleonhardt

examples/rich_tables.py

@@ -109,6 +109,8 @@ def do_countries(self, _: cmd2.Statement) -> None:
                     justify = "right"
                 case gdp if 'GDP' in gdp:
                     justify = "right"
+                case flag if 'Flag' in flag:
+                    justify = "center"
                 case _:
                     justify = "left"