Additional Parameter for Create Payout Proposal Extrinsic: Credit Content WG Budget

## Context

[Payout proposal ](https://github.com/Joystream/pioneer/issues/3073)has an input defined in the designs to allow crediting Content WG budget, but this parameter is missing on the Payout Exstrinsic.

Here's how it looks in the designs:

In this issue we need to extend the Payout Proposal Extrinsic with such parameter

## Scope
- Add parameter to Create Payout Proposal Extrinsic for Credit Content WG budget
- Input is >0.
- Upper bound limited only by council budget at the time of execution

┆Issue is synchronized with this [Asana task](https://app.asana.com/0/1202078489349362/1203411204928805) by [Unito](https://www.unito.io)