Add RRID for PyNWB

[oruebel]

Motivation

Add RRID for citing PyNWB to the docs

Checklist

• Did you update CHANGELOG.md with your changes?
• Have you checked our Contributing document?
• Have you ensured the PR clearly describes the problem and the solution?
• Is your contribution compliant with our coding style? This can be checked running flake8 from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using "Fix #XXX" notation where XXX is the issue number? By including "Fix #XXX" you allow GitHub to close issue #XXX when the PR is merged.

[codecov]

Codecov Report

Merging #1372 (5b350b8) into dev (ef55da0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev    #1372   +/-   ##
=======================================
  Coverage   73.53%   73.53%           
=======================================
  Files          37       37           
  Lines        2331     2331           
  Branches      357      357           
=======================================
  Hits         1714     1714           
  Misses        556      556           
  Partials       61       61           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ef55da0...5b350b8. Read the comment docs.