x/website: include release dates in release notes

[hyangah]

Release history page already presents the release date for each release.
https://go.dev/doc/devel/release

However, the main release notes don't include the release date info.
e.g https://go.dev/doc/go1.12

It will be convenient if the dates (at least years/months) are present.

[seankhliao]

also #40488

[dmitshur]

Observing that, ironically, we have the expected approximate release date for upcoming major releases (e.g., https://tip.golang.org/doc/go1.24 currently says "Go 1.24 is expected to be released in February 2025."). And then it's deleted right as the exact release date becomes known with certainty, when the release is out. (E.g., the "expected to be released in August 2024" was deleted in today's change that dropped the draft notice).

It could be kept and updated to the exact day instead. Perhaps something like:

The latest Go release, version 1.23, arrives on August 13, 2024, six months after Go 1.22. Most of its changes are in […]

[3052]

still missing from current version

https://go.dev/doc/go1.24

[gopherbot]

Change https://go.dev/cl/654015 mentions this issue: _content/doc/go1.24: add release date