[INFRA] Add json describing filename convention

[tsalo]

Closes #133. Note that this configuration file is not used for anything just yet.

Changes proposed in this pull request:

• Add json describing filename convention based on pybids' configuration file.

[codecov]

Codecov Report

Merging #338 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #338   +/-   ##
=======================================
  Coverage   82.27%   82.27%           
=======================================
  Files          37       37           
  Lines        3831     3831           
=======================================
  Hits         3152     3152           
  Misses        679      679           

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