Give a tip for something new; no finder's fee will be taken.

The dispatch origin for this call must be _Signed_ and the signing account must be a
member of the `Tippers` set.

- `reason`: The reason for, or the thing that deserves, the tip; generally this will be
  a UTF-8-encoded URL.
- `who`: The account which should be credited for the tip.
- `tip_value`: The amount of tip that the sender would like to give. The median tip
  value of active tippers will be given to the `who`.

Emits `NewTip` if successful.

# <weight>
- Complexity: `O(R + T)` where `R` length of `reason`, `T` is the number of tippers.
  - `O(T)`: decoding `Tipper` vec of length `T`. `T` is charged as upper bound given by
    `ContainsLengthBound`. The actual cost depends on the implementation of
    `T::Tippers`.
  - `O(R)`: hashing and encoding of reason of length `R`
- DbReads: `Tippers`, `Reasons`
- DbWrites: `Reasons`, `Tips`
# </weight>

- Problem Statement: Lack of approval for the Polkassembly ReferendumV2.
- Significance: Impacts decision-making and community engagement.
- Proposed Solution: Approve the Polkassembly ReferendumV2.
- Expected Outcomes: Enhanced community participation and improved decision-making processes.

#84 [Small Tipper] Referendum #84