Automatic language detection feature

[6MicheleStingo9]

Added LanguageDetection library, DetectLanguage method, and updated tests

• Added the LanguageDetection library to the project in SmartReader.csproj.
• Added the DetectLanguage method and modified the internal constructor in Article.cs.
• Updated PagesTests.cs to test language detection, even when missing in metadata.

Details:

• The library was chosen for its lightweight package size, unlike non-service-based solutions that would have unnecessarily increased project overhead.
• DetectLanguage method is invoked only when language metadata is absent in the HTML page.
• API key for DetectLanguage library must be set as an environment variable for method functionality, providing a free plan with 1000 requests per day and data upload limit of 1MB per day.
• Additional secret management methods may be implemented following C# specifics.

[lofcz]

To me, this doesn't seem like something that should be included in the base library. It introduces a dependency on a random sass service for a little value, given all this does is a call to their API with metadata.Title ?? Content of an article. Have you considered creating your Contrib module or using models with open weights to achieve the same without depending on a sass service? For example, https://huggingface.co/Mike0307/multilingual-e5-language-detection supports 45 languages with a precision sufficient for many use cases.

PS: whenever awaiting calls in a library code, it's a good practice to use .ConfigureAwait(false) to prevent queuing the task on the original context, the pattern is used in the existing library's code.