Consider moving retroarch-nightly here (from games bucket)

[wyndon]

Using a blank template as the packaging one didn't really fit this situation. Following this issue : Calinou/scoop-games#1269

Traditionally, packages in main or extras have had their nightly versions packaged in the versions bucket. In fact, aside from the few ones that have BOTH their stable and nightly versions in the games bucket, all of them do except RetroArch, which for some reason has its nightly version packaged in the games bucket while having the stable one in extras. @Calinou (maintainer of the games bucket) suggested moving the nightly version, which I find more in line with how Scoop usually works.

Alternatively, we could also move the retroarch package from extras to the games bucket, but considering RetroArch's popularity as a software in general, I feel like it deserves to stay in extras.