[DOC] Example comparing spectral connectivity computed over time or o…

…ver trials (mne-tools#129)

* Added example doc for con over time vs over trial
* Added mne-qt-browser to req_doc
* Added reference bibliography for mirror-game paradigm and theta power among occipital lobe and frontal lobe

---------
Authored-by: glia <[email protected]>
Co-authored-by: Adam Li <[email protected]>

CONTRIBUTING.md

@@ -44,7 +44,7 @@ Now you can finally run the tests by running `pytest` in the
 The documentation can be built using sphinx. For that, please additionally
 install the following:
 
-    $ pip install -r requirements_doc.text
+    $ pip install -r requirements_doc.txt
 
 To build the documentation locally, one can run:
 

doc/references.bib

@@ -238,4 +238,29 @@ @article{StamEtAl2012
   year={2012}, 
   month={Sep}, 
   pages={1415–1428}
-}
+}
+
+ @article{KlimeschEtAl2004,
+  title = {Phase-locked alpha and theta oscillations generate the P1–N1 complex and are related to memory performance},
+  journal = {Cognitive Brain Research},
+  volume = {19},
+  number = {3},
+  pages = {302-316},
+  year = {2004},
+  issn = {0926-6410},
+  doi = {https://doi.org/10.1016/j.cogbrainres.2003.11.016},
+  author = {Wolfgang Klimesch and Bärbel Schack and Manuel Schabus and Michael Doppelmayr and Walter Gruber and Paul Sauseng}
+}
+
+ @article{Zimmermann2022,
+  author = {Zimmermann, Marius and Lomoriello, Arianna Schiano and Konvalinka, Ivana},
+  doi = {10.1098/rsos.211352},
+  issn = {20545703},
+  journal = {Royal Society Open Science},
+  number = {2},
+  publisher = {The Royal Society},
+  title = {{Intra-individual behavioural and neural signatures of audience effects and interactions in a mirror-game paradigm}},
+  url = {https://royalsocietypublishing.org/doi/10.1098/rsos.211352},
+  volume = {9},
+  year = {2022}
+}