Ender 3 Top Rail Camera Mount

I recently added a second camera to my Ender 3 setup, and this one has a tripod mount point. I needed a way to mount this from the top rail and be secure/stable enough to stay in place.

I settled on using [this rail mount](https://www.thingiverse.com/thing:5199629) as my starting point and trimmed it down, adding the hole to accommodate a standard-issue #14 (1/4") threaded bolt for the tripod mount point.

Originally I also modified the [screw part from this Thing](https://www.thingiverse.com/thing:4412164), but I don't use it myself in production since the screw is just a bit too fragile to hold consistently (even at 100% infill). Instead, I use a 1/2" quarter-inch bolt to hold the camera firmly in place. Your mileage may vary, so it's included.

This part keeps my top camera neatly tucked out of the way of everything.