'colon-list-separator' - array with one key and multiple values instead of multiple keys with one value

[pingustar]

Basically I would like to have a similar way to the 'bracket-separator' option but for 'colon-list-separator'

It would look like this:

actions:list=create,delete

instead of

actions:list=create&actions:list=delete

I would be happy to open a PR with this feature. I can see a few ways to go about this.

Option 1: adding a new arrayFormat
Option 2: adding a new option to replace the [] bracket with a custom identifier
Option 3: adding a new option to toggle the 'colon-list-separator' format between separated and not separated

What are your thoughts about this?