Mijia button cap builder

Cap builder for Xiaomi Mijia button.


1. Install the [Material Design Icons](https://github.com/Templarian/MaterialDesign-Font) font
* Optionally, you can just download it and add a `use` declaration to the top of the `.scad` file
2. Open the file in [OpenSCAD](https://www.openscad.org/)
3. Use the [MDI cheat sheet](https://pictogrammers.github.io/@mdi/font/5.0.45/) to copy an icon into the "icon" variable in the `.scad`
4. Play around with font size to taste, then export the `.stl` and print!