fix: typo in README (#451)

Author: colesnodgrass

Diff for: README.md

@@ -577,7 +577,7 @@ Both can coexist with standard Tag parsing.
 | `enum:"X,Y,..."`     | Set of valid values allowed for this flag. An enum field must be `required` or have a valid `default`.                                                                                                                                                                                                                         |
 | `group:"X"`          | Logical group for a flag or command.                                                                                                                                                                                                                                                                                           |
 | `xor:"X,Y,..."`      | Exclusive OR groups for flags. Only one flag in the group can be used which is restricted within the same command. When combined with `required`, at least one of the `xor` group will be required.                                                                                                                            |
-| `and:"X,Y,..."`      | Exclsuive AND groups for flags. All flags in the group must be used in the same command. When combined with `required`, all flags in the group will be required.                                                                                                                                                               |
+| `and:"X,Y,..."`      | Exclusive AND groups for flags. All flags in the group must be used in the same command. When combined with `required`, all flags in the group will be required.                                                                                                                                                               |
 | `prefix:"X"`         | Prefix for all sub-flags.                                                                                                                                                                                                                                                                                                      |
 | `envprefix:"X"`      | Envar prefix for all sub-flags.                                                                                                                                                                                                                                                                                                |
 | `set:"K=V"`          | Set a variable for expansion by child elements. Multiples can occur.                                                                                                                                                                                                                                                           |