JOSS request: reference syntax

[bnord]

Line 76, [@\Hu:2001kj] -> @\Hu:2001kj
Line 85-86, Battaglia et al. 2012 [@\Battaglia:2012] -> @\Battaglia:2012
Line 94, Plank:2019 reference is missing; I imagine this is either Planck:2018 or Planck:2018vyg

[bnord]

Derived from #241

[bnord]

updated; passed action checks; will review manuscript when I check other formatting issues.

[bnord]

actually, checked now. it's good. merging.