Add glossary

[TomDonoghue]

Related to #138 - this is place for us to broadly work on and discuss a potential glossary.

So far I just added a sphinx style glossary file, and a really quick scan collecting some terms that could potentially go into it.

The idea is that we can somewhat crowdsource this glossary - so if you have a suggested term or definition - throw it here! In terms of scope, this glossary should be fairly light on the level of detail, offering just a quick definition, but link out to as many resources as we can find to help find and scaffold support for DSP and it's neuroscience applications.

[TomDonoghue]

Collection of Resources to link to:

General DSP:

• Circles, Sines and Signals
  • https://jackschaedler.github.io/circles-sines-signals/

Filtering:

• MNE on filtering
  • https://martinos.org/mne/stable/auto_tutorials/plot_background_filtering.html
• Digital filter design for electrophysiological data
  • https://www.sciencedirect.com/science/article/pii/S0165027014002866

1/f Properties:

• Scholarpedia
  • http://www.scholarpedia.org/article/1/f_noise

[voytek]

I'm approving this as-is, since I see it as a living document. I have links and other bits I can add, but I'll do so later, once I have time to collect all my thoughts and resources.

[TomDonoghue]

@rdgao : if you want to give this a once-over that I didn't write in anything totally ludicrous, then I'll merge it as a first draft (that we can edit / amend as we go).

[rdgao]

minor comments, otherwise looks great

[TomDonoghue]

Thanks for the comments @rdgao

I pushed updates based on these comments. Most things are straight-forward, and I fixed up the powerlaw / 1/f part a bit, if you want to eyeball that and see if it tracks better now.