Add Throw operator

[viceroypenguin]

This PR migrates the Throw operator from System.Interactive.

Fixes #245

[codecov]

Codecov Report

Base: 87.17% // Head: 87.21% // Increases project coverage by +0.03% 🎉

Coverage data is based on head (5780c29) compared to base (03fe7d1).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@                      Coverage Diff                       @@
##           replace-System.Interactive     #247      +/-   ##
==============================================================
+ Coverage                       87.17%   87.21%   +0.03%     
==============================================================
  Files                             210      211       +1     
  Lines                            6162     6165       +3     
  Branches                         1430     1430              
==============================================================
+ Hits                             5372     5377       +5     
+ Misses                            440      438       -2     
  Partials                          350      350              

Impacted Files	Coverage Δ
Source/SuperLinq/Throw.cs	100.00% <100.00%> (ø)
Source/SuperLinq.Async/ConcurrentMerge.cs	98.71% <0.00%> (+2.56%)	⬆️

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