Slope is not enough to exclude mountainous areas

[irm-codebase]

Describe the bug
The module seems to include mountainous areas even when slope's of max: 5° are selected.

Steps to reproduce
Steps to reproduce the behavior:

1. Run for mountainous countries (ITA, CHE) with slope set to a max of 5.7° (common for onshore).
2. Check the produced images. Mountainous zones will have assigned

Expected behavior
Slope is useful, but it might not be enough to exclude some areas near peaks.
I suggest adding a new option, like the Terrain Ruggedness Index (TRI), Topographic Position Index (TPI) or Vector Ruggedness Measure (VRM) in this study:

• https://www.nature.com/articles/sdata201840
• https://www.earthenv.org/topography

These are open and generally accessible and have a resolution of 1km.

Screenshots
See this result for onshore wind in Italy:

The northern border is the Alps. I doubt a lot of wind is going to be placed there.

Environment (please complete the following information):

• OS: Fedora 44
• version: 1.0.0

[irm-codebase]

Turns out this was a bug introduced in #18 due to a typo in the slope renaming. Not an issue!