Feature request: Ergo-L layout

**Is your feature request related to a problem? Please describe.**
There is no support for the Ergo-L layout.

**Describe the solution you'd like**
An implementation of Ergo-L. Ideally though, this project should not require manual implementation of every layout.

Start by locating how existing keyboard layouts are defined and rendered in OverKeys, then compare those entry points with the Ergo-L layout requirements. Done means the application supports selecting and visualizing Ergo-L; the broader goal of avoiding manual implementation may require clarification before work begins.

Written by the indexing model from the issue text.