Add recognizion configuration

[henrivain]

Add TessEngine configuration to ITesseract

Fixes issue #16

• TessEngine can now be configured with EngineConfiguration

  Action<ITessEngineConfigurable>? TesseractOcrMaui.ITesseract.EngineConfiguration { set; }

Improved code quality

• Better information in result from known issue #17 with KnownIssueException

Updated examples in Mainpage.xaml.cs

• Added example of engine configuration action

  
  private async void DEMO_Recognize_AsConfigured(object sender, EventArgs e)
  {
  // Select image (Not important)
  var path = await GetUserSelectedPath();
  if (path is null)
  {
      return;
  }
  
  Tesseract.EngineConfiguration = (engine) =>
  {
      // Engine uses DefaultSegmentationMode, if no other is passed as method parameter.
      // If ITesseract is injected to page, this is only way of setting PageSegmentationMode.
      // PageSegmentationMode defines how ocr tries to look for text, for example singe character or single word.
      // By default uses PageSegmentationMode.Auto.
      engine.DefaultSegmentationMode = TesseractOcrMaui.Enums.PageSegmentationMode.SingleLine;
  
      engine.SetCharacterWhitelist("abcdefgh");   // These characters ocr is looking for
      engine.SetCharacterBlacklist("abc");        // These characters ocr is not looking for
      // Now ocr should be only finding characters 'defgh'
  };
  
  // Recognize image 
  var result = await Tesseract.RecognizeTextAsync(path);
  
  // For this example I reset engine configuration, because same Object is used in other examples
  Tesseract.EngineConfiguration = null;
  
  // Show output (Not important)
  ShowOutput("FromPath, Configured", result);

}