Support optional Value class as literal

[cchantep]

No description provided.

[codecov]

Codecov Report

Merging #623 (025dd9b) into master (29d8d15) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #623      +/-   ##
==========================================
+ Coverage   95.15%   95.20%   +0.04%     
==========================================
  Files          65       65              
  Lines        1157     1168      +11     
  Branches        8        7       -1     
==========================================
+ Hits         1101     1112      +11     
  Misses         56       56              

Flag	Coverage Δ
2.12.15	95.20% <100.00%> (+0.04%)	⬆️
2.13.8	95.73% <90.90%> (-0.05%)	⬇️

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Impacted Files	Coverage Δ
...t/src/main/scala/frameless/functions/package.scala	100.00% <100.00%> (ø)

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[pomadchin]

🎉 a bit tricky overload though, nice that it works.