docs: add Errors section in transloadit plugin doc

website/src/docs/transloadit.md

@@ -10,7 +10,7 @@ category: 'File Processing'
 The `@uppy/transloadit` plugin can be used to upload files to [Transloadit](https://transloadit.com/) for all kinds of processing, such as transcoding video, resizing images, zipping/unzipping, [and much more](https://transloadit.com/services/).
 
 > If you're okay to trade some flexibility for ergonomics, consider using
-> the [Robodog](/docs/robodog/) Plugin instead, which is a higher-level abstraction for 
+> the [Robodog](/docs/robodog/) Plugin instead, which is a higher-level abstraction for
 > encoding files with Uppy and Transloadit.
 
 <a class="TryButton" href="/examples/transloadit/">Try it live</a>
@@ -274,6 +274,18 @@ strings: {
 }
 ```
 
+## Errors
+
+If an error occurs when an Assembly has already started, you can find the Assembly Status on the error object's `assembly` property.
+
+```js
+uppy.on('error', (error) => {
+  if (error.assembly) {
+    console.log(`${error.assembly.assembly_id} failed!`)
+  }
+})
+```
+
 ## Events
 
 ### `transloadit:assembly-created`