Conditionally set default esc_delay of inkey() from environment

[Jeff Quast]

from #156 (comment)

• We should honor this lesser known ESCDELAY environment value as the default value of Terminal.inkey(esc_delay) if set, https://stackoverflow.com/a/28020568 and https://invisible-island.net/ncurses/man/ncurses.3x.html

Specifies the total time, in milliseconds, for which ncurses will await a character sequence, e.g., a function key. The default value, 1000