- took another pass at this function to simplify it. mainly, made
- plot_heatmap_array private

- added a second eyelink dataset for a heatmap tutorial

- added a new tutorial for plotting eyetracking heatmaps
- included a brief example of heatmap plotting in current tutorial

- the alpha parameter was missing from the docstring which caused a numpydoc error

- This is a tough one. In the "working with eye tracker data" tut, I DO want to baseline correct the pupil channel, but I DONT want to baseline correct eyegaze channels. I am not sure that it EVER makes sense to baseline correct eyegaze channels, given that they USUALLY represent a gaze coordinate, but I need to think about this more.
- I may open a separate ticket about this matter

Co-authored-by: Eric Larson <larson.eric.d@gmail.com>

- Use a smarter way to find gaze position channels, dont rely on the ch_name
- No need to mask out values outside the width and height, histogram2d will do it for you
- remove bin_width parameter in favor of relying on sigma param

Co-authored-by: Eric Larson <larson.eric.d@gmail.com>

for more information, see https://pre-commit.ci

- I added a new entry into the doc_dict in mne.utils.doc for the matplotlib cmap parameter, which I believe could prove to be useful elsewhere, for example in mne.viz.misc.plot_csd. FWIW The cmap_topo docstring that was already in the doc_dict says that if None is passed then "reds" will be used. But For any mne functions that have cmap=None as the default, if None is passed into the matplotlib function, the default will actually be whatever matplotlib's default is, which is usually viridis.

- memory profiling revealed that this tutorial was using around 700mb of memory.

Co-authored-by: Daniel McCloy <dan@mccloy.info>
Co-authored-by: Mathieu Scheltienne <mathieu.scheltienne@gmail.com>

- Had to fix conflict in "mne/viz/__init__" because prior PR changed the init files to work better with lazy loader. Just accepted incomign change

Co-authored-by: Daniel McCloy <dan@mccloy.info>

Co-authored-by: Daniel McCloy <dan@mccloy.info>