[ENH] (Re)implement complex data support for Spectrum and `Spectrum…

…Array` classes (#12747)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Eric Larson <larson.eric.d@gmail.com>
Co-authored-by: Daniel McCloy <dan@mccloy.info>
Co-authored-by: Alex Rockhill <aprockhill@mailbox.org>

doc/changes/devel/12747.newfeature.rst

@@ -0,0 +1,3 @@
+Add support for storing Fourier coefficients in :class:`mne.time_frequency.Spectrum`,
+:class:`mne.time_frequency.EpochsSpectrum`, :class:`mne.time_frequency.SpectrumArray`,
+and :class:`mne.time_frequency.EpochsSpectrumArray` objects, by `Thomas Binns`_.