Long Term Support (LTS) policy/guidelines for Smarty 4 (As we start planning for Smarty 6)

[marclaporte]

Planning for Smarty 6 has started:
#1200

Smarty 5 was released in 2024 and is going on strong. Latest release is 5.8.4:
https://github.com/smarty-php/smarty/releases/tag/v5.8.4

Even Smarty 4 (from 2021) is still getting security releases!
https://github.com/smarty-php/smarty/releases/tag/v4.5.7

@juangacovas wrote "Thanks for continuing support for Smarty 4, some are still using it successfully with php 8+ versions":
#1185

So what does support mean? And for how long?

For Smarty 4 LTS, I suppose we are more in a security fix situation as per:
https://pointieststick.com/2026/05/23/long-term-support-doesnt-mean-what-you-think/

So OK for small changes like:
#1185

But maybe not bigger changes like:
#1147

The answer to this question could better inform this PR: #1201