Simple filter to prefix all items from a list. Default prefix will be `--` but you can also pass a custom one.

## Example

```Yaml
my_list:
  - item1
  - item2

{{ my_list | prefix | join(' ') }}

# result:
# "--item1 --item2"
```

Or pass a custom prefix:

```Yaml
my_list:
  - item1
  - item2

{{ my_list | prefix(prefix='-') | join(' ') }}

# result:
# "-item1 -item2"
```