View Controllers: add `SplitViewController`

[compnerd]

[codecov[bot]]

Codecov Report

Merging #656 (63a1e3d) into main (b37d147) will increase coverage by 0.86%. The diff coverage is 50.60%.

:exclamation: Current head 63a1e3d differs from pull request most recent head 63ac785. Consider uploading reports for the commit 63ac785 to get more accurate results

@@            Coverage Diff             @@
##             main     #656      +/-   ##
==========================================
+ Coverage   26.17%   27.03%   +0.86%     
==========================================
  Files         129      130       +1     
  Lines        5120     5322     +202     
==========================================
+ Hits         1340     1439      +99     
- Misses       3780     3883     +103     

Impacted Files	Coverage Δ
...View Controllers/SplitViewControllerDelegate.swift	0.00% <0.00%> (ø)
...ftWin32/View Controllers/SplitViewController.swift	57.27% <57.27%> (ø)
...ces/SwiftWin32/Views and Controls/DatePicker.swift	0.00% <0.00%> (-96.43%)	:arrow_down:
...iftWin32/App and Environment/TraitCollection.swift	68.00% <0.00%> (-9.05%)	:arrow_down:
Sources/SwiftWin32/CA/Transform3D.swift	0.00% <0.00%> (ø)
Sources/SwiftWin32/Views and Controls/View.swift	39.68% <0.00%> (ø)
Sources/SwiftWin32/Support/Date+Extensions.swift
...s/SwiftWin32/View Controllers/ViewController.swift	32.80% <0.00%> (+11.99%)	:arrow_up:
...s/SwiftWin32/App and Environment/Application.swift	76.47% <0.00%> (+37.69%)	:arrow_up: