Script letter puzzle

A variation of the original [letter puzzle](https://www.thingiverse.com/thing:1021649) by neu3no. I added lowercase letters, using the "Script Ecole 2" education-friendly font. Each tile width is computed according to the font spacing, using arpruss' [fontmetrics](https://www.thingiverse.com/thing:3004457) library. Hooks are covered by the next tile, mainly to avoid bridging issues with some letters (e.g. lowercase 'e'). The tile height and the baseline are adjusted so that all letters completely fit inside the tile with some minimum distance to the edges, and the baseline position is the same for lowercase uppercase so that they work together nicely.

STL files are provided for individual letters, alternatively the OpenScad source file can be used to generate a custom set of tiles with uniform distance between them (to match the letters frequency for a given language).

For generating STL files from source, the above mentioned [fontmetrics](https://www.thingiverse.com/thing:300445