Auto merge of #6863 - daxpedda:patch-1, r=alexcrichton
Auto merge of #6863 - daxpedda:patch-1, r=alexcrichton

Improved docs for `maintenance` options

I thought the lack of clear meanings for the available options could use some improvement.
Basically an upgrade of #4431.

Got the relevant text from rust-lang/crates.io#704 and the corresponding [rfc](https://github.com/rust-lang/rfcs/blob/master/text/1824-crates.io-default-ranking.md)

*Questions*
1. Should I put the descriptions outside of the code block?
2. I copied the wording including "maintainer" and "author", should I replace it with "you" or something more appropriate?

rust-lang/cargo,rust-lang/cargo,rustyhorde/cargo,rustyhorde/cargo,vojtechkral/cargo,rust-lang/cargo,nipunn1313/cargo,vojtechkral/cargo,eminence/cargo,nipunn1313/cargo,nipunn1313/cargo,rustyhorde/cargo,tsurai/cargo,tsurai/cargo,tshepang/cargo,tsurai/cargo,eminence/cargo,tsurai/cargo,tshepang/cargo,eminence/cargo,eminence/cargo,rustyhorde/cargo,vojtechkral/cargo,rust-lang/cargo,nipunn1313/cargo,vojtechkral/cargo,tsurai/cargo,tshepang/cargo,tshepang/cargo