Integrate with State of Rust.

[XAMPPRocky]

In a recent release team meeting we discussed having rfcbot take over the manual curation of State of Rust. Ths'd require commands to change the What's next?, move between columns, and add to State of Rust on RFC approval and merge.

[Centril]

So what we could do is have an rfcbot command @rfcbot status STATUS_DESCRIPTION_LINE which updates a new SQL column in the database for issues/PRs; Then, rfcbot will scan all issues labeled C-tracking-issue and add them to the project board if not there, and if they have changed label from B-RFC-Approved to B-unstable or something like that, it is also moved between the columns on the board.

[Centril]

Also cc #198 for an even more automated experience re. automatically making tracking issues.