Add a separate ground-snapping option

This used to be controlled by the y-axis-lock setting.

macrovision.js

@@ -507,7 +507,7 @@ function constrainRel(coords) {
 function snapPos(coords) {
     return {
         x: coords.x,
-        y: (!config.lockYAxis || altHeld) ? coords.y : (Math.abs(coords.y) < config.height.toNumber("meters")/20 ? 0 : coords.y)
+        y: (!config.groundSnap || altHeld) ? coords.y : (Math.abs(coords.y) < config.height.toNumber("meters")/20 ? 0 : coords.y)
     };
 }
 
@@ -2673,6 +2673,18 @@ const settingsData = {
             }
         }
     },
+    "ground-snap": {
+        name: "Snap to Ground",
+        desc: "Snap things to the ground",
+        type: "toggle",
+        default: true,
+        get value() {
+            return config.groundSnap;
+        },
+        set value(param) {
+            config.groundSnap = param;
+        }
+    },
     "axis-spacing": {
         name: "Axis Spacing",
         desc: "How frequent the axis lines are",