Add new game *Arithmetic Progression*

Author: Виталий

README.md

@@ -6,3 +6,6 @@
 <a href="https://asciinema.org/a/697024" target="_blank"><img src="https://asciinema.org/a/697024.svg" /></a>
 A demonstration. The game is to find the greatest common divisor.
 <a href="https://asciinema.org/a/697048" target="_blank"><img src="https://asciinema.org/a/697048.svg" /></a>
+
+Demonstration of the arithmetic progression game
+<a href="https://asciinema.org/a/697128" target="_blank"><img src="https://asciinema.org/a/697128.svg" /></a>

pyproject.toml

@@ -25,3 +25,4 @@ brain-games = 'brain_games.scripts.brain_games:main'
 brain-even = 'brain_games.scripts.brain_even:main'
 brain-calc = 'brain_games.scripts.brain_calc:main'
 brain-gcd = 'brain_games.scripts.brain_gcd:main'
+brain-progression = 'brain_games.scripts.brain_progression:main'