[Feature request] Select multiple Multipart files in one parameter

- Insomnia Version: 6.6.2 (6.6.2.2932)
- Operating System: macOS Mojave 10.14.6 (18G87)

## Details

I am trying to create a POST request with Multipart Form Body and uploading multiple files in the same key/value pair. Insomnia doesnt seem to allow me to select multiple files. I could successfully do it in another REST Client. Is this a limitation or am I doing it wrong?

Sample curl command :

```
curl -X POST \
\
-H ‘cache-control: no-cache’ \
-H ‘content-type: multipart/form-data; \
-F =@ \
-F =@ \
-F =@
```

The issue names no files or tests. Start by reproducing multipart form-body file selection with several files under one key, then trace the file-picker and request-building entry points. Done means multiple files can be selected for one parameter and the generated request matches the supplied curl example.

Written by the indexing model from the issue text.