Use BibTeX citations in documentation

[tsalo]

Closes #665.

Changes proposed:

• Replace references sections with footbibliographies.
• Add sphinxcontrib-bibtex to doc dependencies.

[codecov]

Codecov Report

Merging #670 (252c71d) into main (83d9f55) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #670   +/-   ##
=======================================
  Coverage   85.28%   85.28%           
=======================================
  Files          40       40           
  Lines        4513     4513           
=======================================
  Hits         3849     3849           
  Misses        664      664           

Impacted Files	Coverage Δ
nimare/annotate/cogat.py	91.35% <ø> (ø)
nimare/annotate/gclda.py	97.35% <ø> (ø)
nimare/annotate/lda.py	100.00% <ø> (ø)
nimare/decode/continuous.py	94.73% <ø> (ø)
nimare/decode/discrete.py	96.61% <ø> (ø)
nimare/decode/encode.py	85.18% <ø> (ø)
nimare/meta/cbma/ale.py	94.08% <ø> (ø)
nimare/meta/cbma/base.py	96.52% <ø> (ø)
nimare/meta/cbma/mkda.py	97.02% <ø> (ø)
nimare/meta/ibma.py	100.00% <ø> (ø)
... and 2 more

---

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 83d9f55...252c71d. Read the comment docs.