Annotations extras (#13228)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Alexandre Gramfort <alexandre.gramfort@m4x.org>
Co-authored-by: Daniel McCloy <dan@mccloy.info>
Co-authored-by: Eric Larson <larson.eric.d@gmail.com>

Author: 5 people

doc/changes/devel/13228.newfeature.rst

@@ -0,0 +1 @@
+Add an ``extras`` attribute to :class:`mne.Annotations` for storing arbitrary metadata, by `Pierre Guetschel`_.

doc/changes/names.inc

@@ -234,6 +234,7 @@
 .. _Peter Molfese: https://github.com/pmolfese
 .. _Phillip Alday: https://palday.bitbucket.io
 .. _Pierre Ablin: https://pierreablin.com
+.. _Pierre Guetschel: https://github.com/PierreGtch
 .. _Pierre-Antoine Bannier: https://github.com/PABannier
 .. _Ping-Keng Jao: https://github.com/nafraw
 .. _Proloy Das: https://github.com/proloyd