[client] Add docs for asset uploads

packages/@sanity/client/README.md

@@ -246,6 +246,87 @@ client.mutate(transaction)
 
 An important note on this approach is that you cannot call `commit()` on transactions or patches instantiated this way, instead you have to pass them to `client.mutate()`
 
+### Uploading assets
+
+Assets can be uploaded using the `client.assets.upload(...)` method.
+
+```
+client.asset.upload(type: 'file' | image', body: File | Blob | NodeStream): Promise<AssetDocument>
+```
+
+Read more about [assets in Sanity](https://sanity.io/docs/http-api/assets)
+
+#### Examples: Uploading assets from Node.js
+```js
+// Upload a file from the file system
+client.assets.upload('file', fs.createReadStream('myFile.txt'))
+  .then(document => {
+    console.log('The file was uploaded!', document)
+  })
+  .catch(error => {
+    console.error('Upload failed:', error.message)
+  })
+````
+```js
+
+// Upload an image file from the file system
+client.assets.upload('image', fs.createReadStream('myImage.jpg'))
+  .then(document => {
+    console.log('The image was uploaded!', document)
+  })
+  .catch(error => {
+    console.error('Upload failed:', error.message)
+  })
+```
+
+#### Examples: Uploading assets from the Browser
+```js
+// Create a file with "foo" as its content
+const file = new File(["foo"], "foo.txt", {type: "text/plain"})
+// Upload it
+client.assets.upload('file', file)
+  .then(document => {
+    console.log('The file was uploaded!', document)
+  })
+  .catch(error => {
+    console.error('Upload failed:', error.message)
+  })
+````
+
+```js
+// Draw something on a canvas and upload as image
+const canvas = document.getElementById('someCanvas')
+const ctx = canvas.getContext('2d');
+ctx.fillStyle = '#f85040'
+ctx.fillRect(0, 0, 50, 50);
+ctx.fillStyle = '#fff'
+ctx.font = '10px monospace'
+ctx.fillText('Sanity', 8, 30)
+canvas.toBlob(uploadImageBlob, 'image/png')
+
+function uploadImageBlob(blob) {
+  client.assets.upload('image', blob, "image/png")
+    .then(document => {
+      console.log('The image was uploaded!', document)
+    })
+    .catch(error => {
+      console.error('Upload failed:', error.message)
+    })
+}
+```
+### Deleting an asset
+
+```
+client.assets.delete(type: 'image' | 'file', id: string): Promise
+```
+
+```js
+client.assets.delete('image', '1a2b3c')
+  .then(result => {
+    console.log('deleted imageAsset', result)
+  })
+```
+
 ### Get client configuration
 
 ```js