Add support for set/reset screen mode

ANSI.SYS supports set screen mode ('h') and reset screen mode ('I')
escape sequences. Although we skip them, parse them properly to fix
rendering issues in some Blocktronics AWAKEN artpack ANSIs.

Signed-off-by: Pekka Enberg <penberg@kernel.org>
Fix unknown escape sequence parsing

Stop parsing in csi_sequence() when we encounter unknown escape
sequences to avoid attempting to parse data as escape sequences.

Signed-off-by: Pekka Enberg <penberg@kernel.org>
Use left and right arrow keys for navigating

Signed-off-by: Pekka Enberg <penberg@kernel.org>