fix depthbias slope in wireframe

Author: ChrLackner

ngsolve_webgpu/mesh.py

@@ -331,6 +331,7 @@ def get_shader_code(self):
 
 class MeshWireframe2d(MeshElements2d):
     depthBias: int = 0
+    depthBiasSlopeScale: float = 0.
     topology: PrimitiveTopology = PrimitiveTopology.line_strip
     color = (0, 0, 0, 1)
     fragment_entry_point: str = "fragmentWireframe2d"