Major changes

The compiler team uses the major change process, which requires:

• An issue
• A second

We have supporting automation for both parts.

First, on the rust-lang/compiler-team repository, an issue with the major-change label is created via the template. Once that's opened, it automatically gains the "to-announce" label which should be removed when it's announced at a compiler team meeting.

For seconds, you tell rustbot @rustbot seconded or @rustbot second and it will apply the relevant label. Only team members can do so.

Configuration:

[major-change]
second_label = "final-comment-period"
meeting_label = "to-announce"
# can be found by looking for the first number in URLs, e.g. https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler
zulip_stream = 131828