Fix/documentation builds

[brainandforce]

For some reason, Documenter.jl reliably fails to build the documentation for this package, and I need to fix it - here are the attempts (using CI runs for this testing).

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (b9c1d69) 58.07% compared to head (8fdbd04) 58.07%.

❗ Current head 8fdbd04 differs from pull request most recent head f6994e4. Consider uploading reports for the commit f6994e4 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #186   +/-   ##
=======================================
  Coverage   58.07%   58.07%           
=======================================
  Files          19       19           
  Lines        1405     1405           
=======================================
  Hits          816      816           
  Misses        589      589           

Files	Coverage Δ
src/data/bands.jl	0.00% <ø> (ø)
src/lattices.jl	74.11% <100.00%> (ø)
src/software/vasp.jl	52.26% <ø> (ø)
src/data/kpoints.jl	70.27% <0.00%> (-1.96%)	⬇️
src/data/wavefunctions.jl	58.73% <0.00%> (ø)
src/data/grids.jl	57.04% <0.00%> (ø)

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