Add ElecFeX to analysis tools

[rly]

ElecFeX is a MATLAB-based Electrophysiological Feature eXtraction toolkit for current-clamp recordings. The graphical user interface (GUI) of ElecFeX was designed to analyze electrophysiological recordings in an intuitive and efficient way so as to be accessible to everyone no matter their level of expertise.

Documentation: https://github.com/XinyueMa-neuro/ElecFeX
Paper: https://www.biorxiv.org/content/10.1101/2023.05.27.542584v1
Install via MATLAB Apps interface or from https://www.mathworks.com/matlabcentral/fileexchange/130144-elecfex

It looks like current clamp data in NWB can be read. However, I could not run ElecFeX on MATLAB Online or MATLAB installed locally to test this out. See XinyueMa-neuro/ElecFeX#1