Update availability for all extensions for consistency

[master-nevi]

Several extensions were missing the @available attributes.

[codecov]

Codecov Report

Merging #127 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #127   +/-   ##
=======================================
  Coverage   72.52%   72.52%           
=======================================
  Files           9        9           
  Lines         921      921           
=======================================
  Hits          668      668           
  Misses        253      253           

Flag	Coverage Δ
#ios	70.35% <ø> (ø)
#macos	73.62% <ø> (ø)

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Impacted Files	Coverage Δ
SDWebImageSwiftUI/Classes/Image.swift	40.90% <ø> (ø)
SDWebImageSwiftUI/Classes/ImageManager.swift	69.84% <ø> (ø)
SDWebImageSwiftUI/Classes/ImageViewWrapper.swift	87.09% <ø> (ø)

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[dreampiggy]

These API is not public API. So it does not effect the lower firmware compatibility.

Anyway, it's OK.