Allow copying scalars

[mateuszbaran]

Fixes copy of numbers reported here: https://github.com/JuliaManifolds/Manopt.jl/pull/236#issuecomment-1501881458 .

[codecov[bot]]

Codecov Report

Merging #154 (c3c133f) into master (57abbeb) will decrease coverage by 0.08%. The diff coverage is 100.00%.

:exclamation: Current head c3c133f differs from pull request most recent head 3fec205. Consider uploading reports for the commit 3fec205 to get more accurate results

@@            Coverage Diff             @@
##           master     #154      +/-   ##
==========================================
- Coverage   99.92%   99.84%   -0.08%     
==========================================
  Files          19       19              
  Lines        2532     2535       +3     
==========================================
+ Hits         2530     2531       +1     
- Misses          2        4       +2     

Impacted Files	Coverage Δ
src/ManifoldsBase.jl	98.36% <100.00%> (-1.22%)	:arrow_down:

... and 1 file with indirect coverage changes

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[kellertuer]

L/nearly)GTM, just I do not see where we lost the 2 lines codecov?

[mateuszbaran]

No idea. The new methods are covered so I'd just ignore codecov this time.