feat(textarea): using viewport's left gutter func

[caarlos0]

very very very very very wip

goal is to:

• use the gutter func to show line numbers
• will probably lead to using viewports soft wrap as well

no idea if fully possible, honestly, as there's the whole text navigation involved.

we might also want to, now that we have horizontal scrolling, to allow scrolling instead of wrapping.

anyway, line numbers kind work, impl still bad, just experimenting