Attaching CSV File to Page Throws Mime Type Error

I have a client that edits their data in Excel, exports to CSV, and uploads to a Grav page (default dropzone). After upgrading to 1.7.30, they started getting the following error when uploading the CSV:

> An error occurred while trying to upload the file EV ZX All Parts REV 2.csv. The mime type does not match to file extension`.

The issue was resolved by copying `system/mime.yaml` to `user/config/mime.yaml` (thanks, @mahagr!) and editing the CSV mime type as follows:

```
csv:
- text/csv
- application/vnd.ms-excel
```

The Excel->CSV workflow is pretty common, so `system/mime.yaml` should be modified to include MS's vendor-specific mime type.