Fix offscreencanvas undefined (#88)

* Suppress ReferenceError on some environments (i.e. older iOS)

* fix

* fix

* lint

---------

Co-authored-by: yuriha-chan <yuriha.tsuchiura@gmail.com>

packages/frontend/src/workers/test-webgl2.ts

@@ -1,7 +1,13 @@
-const canvas = new OffscreenCanvas(1, 1);
+try {
-const gl = canvas.getContext('webgl2');
+    // throw ReferenceError in Safari <= 16.3
-if (gl) {
+    const canvas = new OffscreenCanvas(1, 1);
-    postMessage({ result: true });
+    const gl = canvas.getContext('webgl2');
-} else {
+    if (gl) {
+        postMessage({ result: true });
+    } else {
+        postMessage({ result: false });
+    }
+} catch (err) {
+    // assert(e instanceof ReferenceError)
     postMessage({ result: false });
 }