Add Buffer overload

[viceroypenguin]

This PR migrates the Buffer operator from System.Interactive.

Fixes #212

[codecov]

Codecov Report

Base: 86.49% // Head: 86.52% // Increases project coverage by +0.03% 🎉

Coverage data is based on head (49a6681) compared to base (8758b8d).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@                      Coverage Diff                       @@
##           replace-System.Interactive     #220      +/-   ##
==============================================================
+ Coverage                       86.49%   86.52%   +0.03%     
==============================================================
  Files                             203      204       +1     
  Lines                            6014     6035      +21     
  Branches                         1391     1396       +5     
==============================================================
+ Hits                             5202     5222      +20     
- Misses                            463      464       +1     
  Partials                          349      349              

Impacted Files	Coverage Δ
Source/SuperLinq/Batch.cs	96.07% <ø> (ø)
Source/SuperLinq/Buffer.cs	100.00% <100.00%> (ø)
Source/SuperLinq/Take.cs	100.00% <0.00%> (ø)
Source/SuperLinq/TrySingle.cs	100.00% <0.00%> (ø)
Source/SuperLinq/SuperEnumerable.cs	82.35% <0.00%> (+4.57%)	⬆️

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