Allocate lattice for non-periodic structures

[awvwgk]

See dftd4/dftd4#91

Needs a release and version bump in dftd4 as well.

[codecov]

Codecov Report

Merging #14 (231be97) into main (2fdeb1f) will decrease coverage by 0.01%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##             main      #14      +/-   ##
==========================================
- Coverage   64.24%   64.22%   -0.02%     
==========================================
  Files          49       49              
  Lines        4094     4095       +1     
  Branches     1332     1333       +1     
==========================================
  Hits         2630     2630              
  Misses        553      553              
- Partials      911      912       +1     

Impacted Files	Coverage Δ
src/mctc/io/structure.f90	43.10% <0.00%> (-0.76%)	⬇️
src/mctc/version.f90	0.00% <ø> (ø)
src/mctc/io/write/vasp.f90	80.95% <100.00%> (ø)

---

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 2fdeb1f...231be97. Read the comment docs.