docs: Update README (#380)

packages/file-handle/README.md

@@ -2,4 +2,43 @@
 
 WASM module that handle file, such as `checksums` method.
 
-* [ ] Nodejs `checksums` need support pass Buffer
+## Usage on Nodejs
+
+```javascript
+const fs = require('fs')
+const { getCheckSums } = require('@bnb-chain/greenfiled-file-handle');
+const fileBuffer = fs.readFileSync('./CHANGELOG.md');
+
+(async () => {
+  const { contentLength, expectCheckSums } = await getCheckSums(fileBuffer);
+})()
+```
+
+Full Code: https://github.com/bnb-chain/greenfield-js-sdk/blob/main/examples/nodejs/storage.js
+
+## Usage on Browser
+
+load wasm:
+
+```html
+<script src="https://unpkg.com/@bnb-chain/[email protected]/dist/browser/umd/index.js"></script>
+<script
+  window.__PUBLIC_FILE_HANDLE_WASM_PATH__ = 'https://unpkg.com/@bnb-chain/[email protected]/dist/node/file-handle.wasm'`,
+  }}
+></script>
+```
+
+execute wasm:
+
+```javascript
+(async () => {
+  // file is from input element
+  const fileBytes = await file.arrayBuffer();
+  const hashResult = await (window as any).FileHandle.getCheckSums(
+    new Uint8Array(fileBytes),
+  );
+  const { contentLength, expectCheckSums } = hashResult;
+})()
+```
+
+Full Code: https://github.com/bnb-chain/greenfield-js-sdk/blob/main/examples/nextjs/src/components/object/create/index.tsx#L63