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 engagement in Polkassembly ReferendumV2 among users.
- Significance: Enhancing user participation and decision-making in the Polkassembly platform.
- Proposed Solution: Implementing a new voting mechanism to increase user involvement.
- Expected Outcomes: Improved user engagement and more informed decision-making processes.

#191 testt

No Active Proposals