Log specific error even if it is not an Error

src/main.ts

@@ -94,7 +94,7 @@ export async function run(): Promise<void> {
     if (error instanceof Error) {
       core.setFailed(error.message)
     } else {
-      core.setFailed('An unexpected error occurred')
+      core.setFailed(`An unexpected error occurred: ${JSON.stringify(error)}`)
     }
   }
 }