Make backgroundTask available for MacOS 10.15

[lucas34]

No description provided.

[codecov]

Codecov Report

Merging #299 into master will decrease coverage by 3.43%.
The diff coverage is 27.77%.

@@            Coverage Diff             @@
##           master     #299      +/-   ##
==========================================
- Coverage   96.02%   92.59%   -3.44%     
==========================================
  Files          28       29       +1     
  Lines        1838     1863      +25     
==========================================
- Hits         1765     1725      -40     
- Misses         73      138      +65     

Impacted Files	Coverage Δ
Tests/SwiftQueueTests/BackgroundTasksTest.swift	0.00% <0.00%> (ø)
Sources/SwiftQueue/JobBuilder.swift	90.00% <100.00%> (-10.00%)	⬇️
Tests/SwiftQueueTests/LoggerTests.swift	100.00% <100.00%> (ø)
Tests/SwiftQueueTests/SwiftQueueBuilderTests.swift	100.00% <100.00%> (ø)
Tests/SwiftQueueTests/SwiftQueueManagerTests.swift	100.00% <100.00%> (ø)
Tests/SwiftQueueTests/TestUtils.swift	97.61% <100.00%> (+0.18%)	⬆️
Sources/SwiftQueue/Constraint+Executor.swift	83.33% <0.00%> (-8.34%)	⬇️
Sources/SwiftQueue/SwiftQueueManager.swift	80.61% <0.00%> (-5.11%)	⬇️