Entry point without TLA for js package (#1638)

Summary:
Follow up on #1637

TLDR: tooling for TLA is not there yet; An additional entry point without top-level-await is appropriate

- adds ./load entry to js package
- uses .js file extensions to prevent requiring [allowImportingTsExtensions](https://www.typescriptlang.org/tsconfig#allowImportingTsExtensions)

Pull Request resolved: #1638

Reviewed By: joevilches

Differential Revision: D55614636

Pulled By: NickGerleman

fbshipit-source-id: 126a94aa68d22d32b938282cfa1a5059bb9df337

Author: bbohlender

javascript/README.md

@@ -29,3 +29,12 @@ node.free();
 ## Requirements
 
 `yoga-layout` requires a toolchain that supports ES Modules and top-level await.
+
+If top-level-await is not supported, use the `yoga-layout/load` entry point instead. This requires to load yoga manually:
+
+```ts
+import {loadYoga, Align} from 'yoga-layout/load';
+
+const node = (await loadYoga).Node.create();
+node.setAlignContent(Align.Center);
+```

javascript/package.json

@@ -11,6 +11,10 @@
   },
   "type": "module",
   "main": "./src/index.ts",
+  "exports": {
+    ".": "./src/index.ts",
+    "./load": "./src/load.ts"
+  },
   "files": [
     "binaries/**",
     "src/**"

javascript/src/load.ts

@@ -0,0 +1,25 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+// @ts-ignore untyped from Emscripten
+import loadYogaImpl from '../binaries/yoga-wasm-base64-esm.js';
+import wrapAssembly from './wrapAssembly.ts';
+
+export type {
+  Config,
+  DirtiedFunction,
+  MeasureFunction,
+  Node,
+  Yoga,
+} from './wrapAssembly.ts';
+
+export async function loadYoga() {
+  return wrapAssembly(await loadYogaImpl());
+}
+export * from './generated/YGEnums.ts';