Sort output to avoid relying on the undefined order of directory content (#57)

Author: d-ronnqvist

Tests/SwiftDocCUtilitiesTests/StaticHostableTransformerTests.swift

@@ -77,7 +77,7 @@ class StaticHostableTransformerTests: StaticHostingBaseTests {
 
         // Test the content of the output folder.
         let expectedContent = ["documentation", "tutorials"]
-        let output = try fileManager.contentsOfDirectory(atPath: outputURL.path)
+        let output = try fileManager.contentsOfDirectory(atPath: outputURL.path).sorted()
 
         XCTAssertEqual(output, expectedContent, "Unexpected output")
         for item in output {