Fix section title extraction logic in DocusaurusContentGenerator

.NET changed how Reverse works

Author: timunie

src/DocusaurusExportPlugin/DocusaurusContentGenerator.cs

@@ -328,7 +328,7 @@ private string EscapeMdxSpecialChars(string content)
                     // We may get more than one line so find the last one with a section title which will be
                     // the closest to the span.
                     string? title = sectionTitle.Value.Split(new[] { '\r', '\n' },
-                        StringSplitOptions.RemoveEmptyEntries).Reverse().FirstOrDefault(
+                        StringSplitOptions.RemoveEmptyEntries).AsEnumerable().Reverse().FirstOrDefault(
                         t => t.Trim().Length > 2 && t[0] == '#');
 
                     if (title != null)
@@ -468,4 +468,4 @@ private void RecursiveCopy(string sourcePath, string destPath, ref int fileCount
                     RecursiveCopy(folder, destPath + folder.Substring(sourcePath.Length + 1), ref fileCount);
         }
     }
-}
+}