Adding sensitivity maps for forward models in mne.report

[1himan]

Reference issue (if any)

Fixes #2828.

What does this implement/fix?

now the report looks something like this:

[tsbinns]

@1himan Just FYI, the :meth: formatting was recently fixed here: #13690
In the first screenshot, you are looking at the stable documentation where this has not been fixed, but if you look at the dev docs online or in your second screenshot, it is fixed (regardless of the newline change).

[1himan]

@1himan Just FYI, the :meth: formatting was recently fixed here: #13690 In the first screenshot, you are looking at the stable documentation where this has not been fixed, but if you look at the dev docs online or in your second screenshot, it is fixed (regardless of the newline change).

nice. I'll change accordingly.

[larsoner]

Don't forget doc/changes/13722.newfeature.rst as well

[larsoner]

@1himan if you push commits to fix, feel free to ping us for re-review. Most folks aren't notified about commit pushes!

One last tweak -- can you modify https://mne.tools/stable/auto_tutorials/intro/70_report.html#adding-a-forward-solution to use sensitivity=True to showcase this feature (and implicitly test it by getting CircleCI to render it)?