Support Braille cursor routing

[jooyoungseo]

We need to support braille cursor routing. This is a feature that allows the user to route the braille cursor to the PC cursor. A successful model is Spark Braille. They also have an open-source GitHub repository here. We can learn from their implementation.

[ellvix]

Just the actual tethering is needed, though we can look at the 2 column patterns and try to implement later, like for line plot.

For now we just need the connection for the physical buttons on the braille display.

[ellvix]

fixed with PR #509