Use OffscreenCanvas types library

Typescript (at  least our current version) is confused about the OffscreenCanvas type. Installing the TS types for it resolves this issue.

Should be reviewed once we update typescript version to 5.x, to see if those extra types are still needed

Author: MonkeyDo

Diff for: frontend/js/src/explore/art-creator/utils.tsx

@@ -35,13 +35,15 @@ export async function svgToBlob(
 
   let blob;
   if ("OffscreenCanvas" in window) {
-    blob = await (canvas as OffscreenCanvas).convertToBlob({
+    canvas = canvas as OffscreenCanvas;
+    blob = await canvas.convertToBlob({
       type: encodeType,
     });
   } else {
     blob = await new Promise<Blob | null>((done, err) => {
       try {
-        (canvas as HTMLCanvasElement).toBlob(done, encodeType);
+        canvas = canvas as HTMLCanvasElement;
+        canvas.toBlob(done, encodeType);
       } catch (error) {
         err(error);
       }

Diff for: package-lock.json

@@ -133,6 +133,7 @@
     "@types/jest": "^29.5.3",
     "@types/less": "^3.0.3",
     "@types/lodash": "^4.14.149",
+    "@types/offscreencanvas": "^2019.7.3",
     "@types/react": "^18.0.25",
     "@types/react-dom": "^18.0.8",
     "@types/react-helmet": "^6.1.11",