PackageToJS: Use non-class type for SwiftRuntime in instantiate.d.ts

Use of class type for `SwiftRuntime` in `instantiate.d.ts` makes it
difficult to union types of two `instantiate` variants.

Author: kateinoigakukun

Plugins/PackageToJS/Templates/instantiate.d.ts

@@ -1,4 +1,6 @@
-import type { /* #if USE_SHARED_MEMORY */SwiftRuntimeThreadChannel, /* #endif */SwiftRuntime } from "./runtime.js";
+/* #if USE_SHARED_MEMORY */
+import type { SwiftRuntimeThreadChannel } from "./runtime.js";
+/* #endif */
 
 /* #if HAS_BRIDGE */
 export type { Imports, Exports } from "./bridge-js.js";
@@ -50,6 +52,12 @@ export interface WASI {
     extractFile?(path: string): Uint8Array | undefined
 }
 
+export type SwiftRuntime = {
+    UnsafeEventLoopYield: { [Symbol.hasInstance]: (value: unknown) => boolean }
+    main(): void;
+    startThread(tid: number, startArg: number): void;
+}
+
 export type ModuleSource = WebAssembly.Module | ArrayBufferView | ArrayBuffer | Response | PromiseLike<Response>
 
 /**