Problem 17 (2022 AMC 8)

If $n$ is an even positive integer, the double factorial notation $n!!$ represents the product of all the even integers from $2$ to $n$. For example, $8!! = 2 \cdot 4 \cdot 6 \cdot 8$. What is the units digit of the following sum? $2!! + 4!! + 6!! + \dots + 2018!! + 2020!! + 2022!!$