End Inserts for Smashing Acrylics Let's Split Case

These are end inserts for [Smashing Acrylics Let's Split Case](https://smashingacrylics.co.uk/product/lets-split-acrylic-cases/) to close off the individual cases and make everything a bit neater. STLs for both the right as well as the left side are included.

These inserts have been designed with a Let's Split in mind, where the TRRS jacks are towards the middle. They have been tested with a case from the [original groupbuy](https://smashingacrylics.co.uk/group-buy-lets-split-thick-acrylic-ca