File Input: Add examples

### Description

It could be nice to add example flows for the new File Input widget.
Flows could be

- Upload a .txt file and show it in debug
- Upload a .csv file and show it in table
- Upload an image file and show it in template and/or in markdown

I'd like to do it, but i think i need some help...

### Have you provided an initial effort estimate for this issue?

I am no FlowFuse team member (Unfortunately ;))