Termion is not supported on Windows, so we need to avoid building it.
Adds a conditional dependency to the Cargo.toml file to only include
termion when the target is not Windows. This allows contributors to
build using the `--all-features` flag on Windows rather than needing
to specify the features individually.
`crossterm`, `termion`, and `termwiz` can now be accessed as
`ratatui::{crossterm, termion, termwiz}` respectively. This makes it
possible to just add the Ratatui crate as a dependency and use the
backend of choice without having to add the backend crates as
dependencies.
To update existing code, replace all instances of `crossterm::` with
`ratatui::crossterm::`, `termion::` with `ratatui::termion::`, and
`termwiz::` with `ratatui::termwiz::`.
Both termion and crossterm backends were not moving the cursor if the first diff to draw was on the
second cell. The condition triggering the cursor move has been updated to fix this. In addition, two
tests have been added to avoid future regressions.
