Change preview npm command to use firebase serve; fix headers

firebase.json

@@ -21,6 +21,19 @@
 						"value": "same-origin"
 					}
 				]
+			},
+			{
+				"source": "**/*",
+				"headers": [
+					{
+						"key": "Cross-Origin-Embedder-Policy",
+						"value": "require-corp"
+					},
+					{
+						"key": "Cross-Origin-Opener-Policy",
+						"value": "same-origin"
+					}
+				]
 			}
 		]
 	}

package.json

@@ -6,7 +6,7 @@
 	"scripts": {
 		"dev": "vite dev",
 		"build": "vite build",
-		"preview": "vite preview",
+		"preview": "firebase serve",
 		"check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
 		"check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
 		"lint": "prettier --plugin-search-dir . --check .",