Canon FD lens adapter for GuerillaBeam

For adapting Canon FD lenses to [GuerillaBeam](https://www.thingiverse.com/thing:692318) projectors (with the ability to focus to infinity).

Unlike the other [GuerillaBeam lens adapters](https://www.thingiverse.com/tag:gBeam-lens-adapter) lens adapters, this one is **not very robust.** (that's why it's separate).

If you'd like to connect an FD lens to GuerillaBeam, I'd rather recommend an adapter to an intermediary lens mount. Focus to infinity can still be achieved this way, by attachi