feature: add cumulative voting type

[elboletaire]

Describe the feature

Like quadratic voting, but with costExponent=1.

Motivation

Being able to properly identify votings of this type. You have an example voting of this type here: https://explorer.vote/process/6b342d99f2187bf87ae56dfceaf3b6531c336365830e460e212d02000000006d

Constraints & Assumptions

Not sure it can be detected easily since we are not storing any metadata for these kind of votings and maybe we should, but that would not make old votings to be available after release. Due to this, it may be a better solution to simply identify it based on the params it already has defined (?).

[marcvelmer]

It's already been there, it's the budget election type.

Quadratic voting has been added in #410 .

[elboletaire]

It's already been there, it's the budget election type.

Quadratic voting has been added in #410 .

Wait, then what's the quadratic example we have in the SDK? 🤔 https://github.com/vocdoni/vocdoni-sdk/blob/main/examples/typescript/src/quadratic.ts