Add a link to major release cadence discussion

Why is this change being made?

Recently a question in Slack was asked: Does anyone here know why we don’t have 12.11 defined as an upcoming milestone? We have 12.10 and 13.0.

Update in this MR adds a more direct mention of the cadence and highlights the maintenance policy where we have this defined. It also links to the issue in which a decision was made for a yearly major release cadence.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what