[SC64][HW] Added small piece to reach the tactile button from the bac…

…k shell (#61)

Adding a small piece to reach the button from the back shell. Fits
great, works well, and doesn't fall out

![button](https://github.com/Polprzewodnikowy/SummerCart64/assets/40926080/f35e3420-af41-4476-81e3-f46825c84245)

![IMG20231221114136](https://github.com/Polprzewodnikowy/SummerCart64/assets/40926080/66868832-cc00-492c-9d95-b3c9fb0c7944)

![IMG20231221114114](https://github.com/Polprzewodnikowy/SummerCart64/assets/40926080/c5c867ce-c1ea-4933-b84f-29746245c92d)