Documentation: Make it easier to check when the next npm release is scheduled

[gziolo]

There are some existing documents which contain the necessary details, but they are hard to discover and aren't properly cross-linked:

• https://github.com/WordPress/gutenberg/blob/master/docs/contributors/release.md#packages-releases-and-wordpress-core-updates
• https://github.com/WordPress/gutenberg/blob/master/packages/README.md#releasing-packages

There is also https://github.com/WordPress/gutenberg/blob/master/docs/designers-developers/developers/packages.md which doesn't contain any reference.

There is also this roadmap issue (#15068) pinned and displayed on the issues page:

We could include the details about the major WordPress releases and how it impacts npm releases.

[paaljoachim]

I am pinging in @noahtallen here.
Should the issue remain open or should we close it?

[gziolo]

I don't think it's improved much.

[noahtallen]

I agree this would be very helpful, especially during the core WP release cycle.