Implemented the "currentFolder" property for the FileService service in the Library target.

Tests/Library/Services/FileServiceTests.swift

@@ -0,0 +1,22 @@
+import Testing
+
+@testable import ColibriLibrary
+
+struct FileServiceTests {
+
+    // MARK: Properties tests
+
+    @Test("Test the file service provides a current folder URL")
+    func currentFolder() async {
+        // GIVEN
+        let service = FileService()
+
+        // WHEN
+        let url = await service.currentFolder
+
+        // THEN
+        #expect(url.path() == "/private/tmp")
+        #expect(url.isFileURL == true)
+    }
+
+}