README fix: $reduce was done, but still documented as TBD

[kix]

Subj.

[mlapshin]

Thanks for your participation, but instead of removing any mentions of $reduce from README, you would better provide an example of $reduce usage.

[kix]

Isn't it documented already? See https://github.com/HealthSamurai/jute.clj#reduce-1
Sincerely hope there's no misunderstanding :)

[kix]

@mlapshin, I see there is a pull request next to this that might look like Hacktoberfest spam, so I'm sorry if mine looked the same to you. Probably I should've opened this in November :)