Improve voting types documentation

[elboletaire]

Our voting-types section needs a revamp: https://developer.vocdoni.io/sdk/integration-details/voting-types

If you access it, you'll see we have a list of voting types, and below, there's a "results interpretation section". This is confusing since, if you click on one of the voting types at the beginning, you'll get to a section where that voting type is properly explained, and there's its own results interpretation section.

I think there's even a voting type repeated: ranked voting. It has its own section, but it's also below in the results interpretation (I'd say is repeated, but both sections should be checked to ensure it's actually the same voting type).

We should create sections for the missing voting types, which are, at least:

• Multiple Question (superseeds Document multichoice elections #136)
• Linear-Weighted
• Ranked-Choice (this is the one that may be duplicated)