core: add nearClippedProjectionMatrix to MLNCustomStyleLayer (#4364)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Bart Louwers <bart@emeel.net>

include/mbgl/style/layers/custom_layer_render_parameters.hpp

@@ -22,8 +22,14 @@ struct CustomLayerRenderParameters {
     double bearing;
     double pitch;
     double fieldOfView;
+
+    /// Standard projection matrix (nearZ = 1 tile unit).
+    /// Use this for 2D/flat custom geometry.
     std::array<double, 16> projectionMatrix;
 
+    /// A 4×4 matrix representing the map view’s current near clip projection state.
+    std::array<double, 16> nearClippedProjectionMatrix;
+
     CustomLayerRenderParameters(const PaintParameters&);
 };