How to: custom mimetypes
change the association of a file extension

using commandline args, you can do something like `--mime gif=image/jif` and `--mime ts=text/x.typescript` (can be specified multiple times)

in a config file, this is the same as:

```yaml
[global]
  mime: gif=image/jif
  mime: ts=text/x.typescript
```

run copyparty with `--mimes` to list all the default mappings