[improve docs]: Sudo Pallet (#1209)

* refactor docs

* add docify

* nit

* add #![deny(missing_docs)]

* Apply suggestions from code review

Co-authored-by: Juan <juangirini@gmail.com>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>

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Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Juan <juangirini@gmail.com>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>