Currently, when pydoclint is called with no arguments, it lints no files and prints a success message. This can be confusing to new users, since there's no indication that nothing was actually checked.

There are two sensible better options here:

(1) When no paths are provided, default to checking the current working directory. This matches the behaviour of e.g. Ruff and Pyright.
(2) When no paths are provided, exit with an error. This matches the behaviour of e.g. Pylint.

In either case, pydoclint should at least print a warning if it exits without checking any files, as this typically indicates something has gone wrong (either the user has not provided any paths or their exclude is excluding all files that would be checked).