1SD (with bump) ALPS/Matias compatible DSA keycap

Matias/ALPS compatible keycap with a spherical top profile.

This deep-dish 1SD has a small, raised bar at the front of the keytop, so you can identify the key by feel alone. This deep-dish keycap is normally used for the home row on a keyboard, and this *bump* version if for the keys where your index fingers rest (`f` and `j` keys on a QUERTY layout). It has a 1.6mm detent depth.

The other 6 deep-dish keys for the home row are available in the 1SD model

Based on the DSA family from Signature Plastics but 3D printed with a 1Z mount (but the mount is flush with the bottom of the keycap to make it more suitable for 3D printing. 

The center mount is connected to the edges by 4 posts that support the post so it is fully supported during printing. These posts have a small notch at each end, so they can be quickly and accurately clipped off using side cutters before fitting. 

This keycap is similar to the dox keycap, buit with an alps-compatible, rather than cherry-compatible key fitting.