Add Workflow.getMemo wrapper method

[grouzen]

Changes being made

Add a wrapper for Workflow.getMemo[T] (typed version)

Additional context

/addresses #88

[codecov-commenter]

Codecov Report

Merging #123 (d15a043) into main (8cc96e7) will increase coverage by 0.21%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #123      +/-   ##
==========================================
+ Coverage   38.35%   38.56%   +0.21%     
==========================================
  Files         115      115              
  Lines        4075     4055      -20     
==========================================
+ Hits         1563     1564       +1     
+ Misses       2512     2491      -21     

Files Changed	Coverage Δ
...c/main/scala/zio/temporal/workflow/ZWorkflow.scala	42.50% <100.00%> (+1.47%)	⬆️

... and 7 files with indirect coverage changes