feat: add enum for OrsSurface encoded value

Author: Sascha Fendrich

core/src/main/java/com/graphhopper/routing/ev/OrsSurface.java

@@ -0,0 +1,24 @@
+// ORS-GH MOD: additional class
+package com.graphhopper.routing.ev;
+
+public enum OrsSurface {
+    // Keep in sync with ORS documentation: surface.md
+    UNKNOWN,
+    PAVED,
+    UNPAVED,
+    ASPHALT,
+    CONCRETE,
+    METAL,
+    WOOD,
+    COMPACTED_GRAVEL,
+    GRAVEL,
+    DIRT,
+    GROUND,
+    ICE,
+    PAVING_STONES,
+    SAND,
+    GRASS,
+    GRASS_PAVER;
+
+    public static final String KEY = "ors_surface";
+}