fix a key error in docs

docs/docs/en.md

@@ -149,7 +149,7 @@ The backend should provide a `session_id` (to identify the upload) and a `end_of
 
 In this phase we'll upload every chunk until all of them are uploaded. This step allows some failures in the backend, and will retry up to `maxRetries` times.
 
-We'll send the `session_id`, `start_chunk` and `chunk` (the sliced blob - part of file we are uploading). We expect the backend to return `{ status: 'success' }`, we'll retry otherwise.
+We'll send the `session_id`, `start_offset` and `chunk` (the sliced blob - part of file we are uploading). We expect the backend to return `{ status: 'success' }`, we'll retry otherwise.
 
 Use the option `uploadBody` to add more parameters to the body of this request.
 

src/chunk/ChunkUploadHandler.js

@@ -44,6 +44,13 @@ export default class ChunkUploadHandler {
     return this.file.size
   }
 
+  /**
+   * Gets the file size
+   */
+  get fileName () {
+    return this.file.name
+  }
+
   /**
    * Gets action (url) to upload the file
    */
@@ -222,7 +229,8 @@ export default class ChunkUploadHandler {
       body: Object.assign(this.startBody, {
         phase: 'start',
         mime_type: this.fileType,
-        size: this.fileSize
+        size: this.fileSize,
+        name: this.fileName
       })
     }).then(res => {
       if (res.status !== 'success') {