Add UI control and state management for god rays source size

src/app/App.tsx

@@ -3238,6 +3238,12 @@ export function App({ store, initialStatusMessage }: AppProps) {
   ] = useState(
     String(editorState.document.world.advancedRendering.godRays.density)
   );
+  const [
+    advancedRenderingGodRaysSourceSizeDraft,
+    setAdvancedRenderingGodRaysSourceSizeDraft
+  ] = useState(
+    String(editorState.document.world.advancedRendering.godRays.sourceSize)
+  );
   const [
     advancedRenderingGodRaysSamplesDraft,
     setAdvancedRenderingGodRaysSamplesDraft
@@ -4316,6 +4322,9 @@ export function App({ store, initialStatusMessage }: AppProps) {
     setAdvancedRenderingGodRaysDensityDraft(
       String(advancedRendering.godRays.density)
     );
+    setAdvancedRenderingGodRaysSourceSizeDraft(
+      String(advancedRendering.godRays.sourceSize)
+    );
     setAdvancedRenderingGodRaysSamplesDraft(
       String(advancedRendering.godRays.samples)
     );
@@ -12582,6 +12591,23 @@ export function App({ store, initialStatusMessage }: AppProps) {
     }
   };
 
+  const applyAdvancedRenderingGodRaysSourceSize = () => {
+    try {
+      applyAdvancedRenderingSettings(
+        "Set god rays source size",
+        "Updated the god rays source size.",
+        (advancedRendering) => {
+          advancedRendering.godRays.sourceSize = readPositiveNumberDraft(
+            advancedRenderingGodRaysSourceSizeDraft,
+            "God rays source size"
+          );
+        }
+      );
+    } catch (error) {
+      setStatusMessage(getErrorMessage(error));
+    }
+  };
+
   const applyAdvancedRenderingGodRaysSamples = () => {
     try {
       applyAdvancedRenderingSettings(