Add `--cycles` option

[evanplaice]

Add the ability to configure the number of times the pomo runs.

Ex

npx pomo -w 50 -b 10 -c 8

This runs the pomodoro runs 8 cycles of 50 minutes work with 10 minutes rest.

This could also be used to run an infinite number of cycles until the app receives a TERM signal with

npx pomo -w 50 -b 10 -c ∞