Allow unsafe_wrapping PointerWrappers to vectors

[JoshuaLampert]

In Trixi.jl we also need to unsafe_wrap to vectors, not only to matrices.

[sloede]

LGTM! Thanks!

[codecov]

Codecov Report

Merging #82 (080057a) into main (d57ae17) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main      #82   +/-   ##
=======================================
  Coverage   15.90%   15.90%           
=======================================
  Files           3        3           
  Lines        1516     1516           
=======================================
  Hits          241      241           
  Misses       1275     1275           

Flag	Coverage Δ
unittests	15.90% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/pointerwrappers.jl	95.45% <100.00%> (ø)

[sloede]

LGTM. You could consider to use different names for the wrapped entities in the tests, eg, vertices_matrix and vertices_vector, to avoid ambiguity.