[v8] Define version support policy & next major schedule

[mydea]

When shipping v8, we want to be more transparent about when (approximately) we plan on shipping v9, as well as what versions we plan on dropping support for then.

This does not need to be an exact date, but something that users can orient around.

I would suggest either a 6 or 9 month period (so ~July or October 2024 for v9).

New Version support in v9:

• Node 16+
• ES2018

Open questions

• What timerange do we want to plan for? 6 months, 9 months, ...?
• Do we plan to keep Node 16 support, or raise this even further?
• Do we want to raise ES support?

I don't think we need to be super strict here, it's mostly about adding a docs page to the repo that outlines our rough plans so that this is somewhat transparent, and it is also helpful for ourselves to kind of know when this will come around and plan accoridngly.

[AbhiPrasad]

Closing this because we've made decisions for generic v8 support. We can think about long term LTS plans after v8 comes out.