[#167] Sentence trainer improvements

[Izeren]

Sentence trainer

1. Expanded text area to allow longer sentences to be visible.
2. Once text is in the area, pressing enter will update url parameters and trigger the next word.
3. The sentence input has a debounce of 5 seconds. If no strokes are pressed within 5 seconds, focus will be switched to the next chord.
4. The default sentence is now longer than 2 words. If it is shorter than n words, the n-gram page will output text saying that it is too short.
5. Resolved circular dependency causing reactivity issues and breaking the page for long sentences.
6. Once the sentence is entered, the focus is automatically switched to the input area.