reactivex.github.io needs a new administrator

[DavidMGross]

I'm no longer able to devote time to maintaining the reactivex.github.io site and its associated ReactiveX repo. There are some outstanding PRs that need review/merging, but in general there hasn't been a whole lot of activity there over the past months, so this is probably not a particularly demanding position.

[saeedntt]

Can you explain a bit more?

[r3h0]

See also ReactiveX/reactivex.github.io#398

[MaratCrash]

@DavidMGross do you need help with that yet?

[t10-13rocket]

@DavidMGross Yes, I need help.