feat: added path normalization to mock file stream

Author: HarrisonTCodes

src/TestableIO.System.IO.Abstractions.TestingHelpers/MockFileStream.cs

@@ -55,6 +55,7 @@ public MockFileStream(
         ThrowIfInvalidModeAccess(mode, access);
 
         this.mockFileDataAccessor = mockFileDataAccessor ?? throw new ArgumentNullException(nameof(mockFileDataAccessor));
+        path = path.Replace(Path.AltDirectorySeparatorChar, Path.DirectorySeparatorChar).TrimSlashes();
         this.path = path;
         this.options = options;