add an underscore to numbered filenames

Here's an example, the file is http://images.neopets.com/cp/items/data/000/000/546/546022_1132b0ffeb/546022.js and the constructor is _546022, to account for the fact that JS syntax won't allow a plain number there.

src/app/components/OutfitCanvas.js

@@ -213,6 +213,9 @@ export function OutfitCanvasMovie({ librarySrc, zIndex }) {
         const fileName = librarySrc.split("/").pop();
         const fileNameWithoutExtension = fileName.split(".")[0];
         constructorName = fileNameWithoutExtension.replace(/[ -]/g, "");
+        if (constructorName.match(/^[0-9]+$/)) {
+          constructorName = "_" + constructorName;
+        }
       } catch (e) {
         console.error(
           `Movie librarySrc %s did not match expected format: %o`,