Integrate synthetic data for text recognition training

[robertknight]

The main improvement needed for Ocrs to be more useful is higher text recognition accuracy / lower error rate, especially with longer lines. Also for multilingual support, examples in more languages will be needed. The main plan to improve this is to expand the training data with synthetic images. There are a number of existing text generation projects that might be useful:

1. https://github.com/ankush-me/SynthText
2. https://github.com/Belval/TextRecognitionDataGenerator (forked here to add Pillow v10 support)
3. https://github.com/clovaai/synthtiger

[robertknight]

The main improvement needed for Ocrs to be more useful is higher text recognition accuracy / lower error rate, especially with longer lines.

This was partly addressed in robertknight/ocrs#32. Long line images are still squashed to 800px during training though, which needs to be fixed.