Propose and approve a spend of treasury funds.

## Dispatch Origin

Must be [`Config::SpendOrigin`] with the `Success` value being at least `amount`.

### Details
NOTE: For record-keeping purposes, the proposer is deemed to be equivalent to the
beneficiary.

### Parameters
- `amount`: The amount to be transferred from the treasury to the `beneficiary`.
- `beneficiary`: The destination account for the transfer.

## Events

Emits [`Event::SpendApproved`] if successful.

- **Problem Statement:** Lack of community engagement in Polkassembly referendums.
- **Significance:** Low participation rates hinder decision-making processes.
- **Proposed Solution:** Encouraging more community involvement through awareness campaigns.
- **Expected Outcomes:** Increased voter turnout and improved decision-making.

#472 Nay - wrong preimage