Make current character visible (when horizontally scrolled away) while typing

[janopae]

After #84 implements horizontal scrolling, you can scroll the current character out of the visible area horizontally. When doing so, starting to type (and other situations that should make the current character visible) don't change the horizontal scrolling.

This should be fixed by turning the makeLineVisible function into a makeCharacterVisible function and adjusting all usages.

[limburgher]

Hello! This repository is merging into https://github.com/trelby/trelby.

Please check your issue against the current code there. If the issue is still relevant, please open a version of this issue there and close this issue. If not, just close this issue.

All issues in this repository that are still open in 30 days will be closed. Thank you!