make a bar plot of retention_7 grouped by version

[a-arad]

• retention_7 is the binary t/f variable that tells us whether the player returned to the game 7 days after the launch of the experiment
• version is the experimental group (gate_30, gate_4)

make a bar plot

[a-arad]

working on it

[a-arad]

good job arad - merged

[a-arad]

done