Proposed documentation enhancement

Hi, just a small suggestion:

Issue

I noticed that that data is given to the tfr_array_multitaper and tfr_array_morlet functions as epoch_data, but as data for tfr_array_stockwell.

All three of these functions state that the data must be of shape (n_epochs, n_channels, n_times), so it is clear that even for tfr_array_stockwell, data should be epoched, however this is not so clear from the Looking at the Time-Frequency module API.

I could see someone skimming the API thinking that tfr_array_multitaper and tfr_array_morlet must be performed on epoched data, but tfr_array_stockwell on raw or epoched data (given the different name of the data argument).

Possible solution

Changing data to epoch_data in tfr_array_stockwell would bring it in line with the other functions and make it clear from even the module API that the Stockwell function expects epoched data.

Cheers,
Thomas!