Upload can't handle more than 1Mb

**Describe the bug**
I'm trying to upload image files using the upload function in the GUI. There seems to be a limit of 1Mb, before there's a "Payload too large" error. Can I increase that limit?

**To Reproduce**
Steps to reproduce the behavior:
1. Go to 'Import'
2. Click on 'Upload files'
3. Select files with a total of more than 1Mb.
4. See error

**Expected behavior**
Posibillity to upload more/larger files.

**Screenshots**

**Environment (please complete the following information):**
- OS: Kubernetes
- Label Studio Version [e.g. 1.14.0]