Docs shotgun 3

* Tweak exclude patterns, which were accidentally excluding qt.console.frontend_widget
* Added example of adding input transformers (#4709)
* Tidied up and added some module docstrings, now that we're using the first line in the API index
* Update the inputsplitter module docstring, which was rather out of date.
* Fix some header levels introduced in #4265
* pyreadline is apparently no longer mandatory on Windows (#4544)