docs: explicit EOL for previous releases

[patak-dev]

Description

We discussed with @sapphi-red and @dominikg about explicitly documenting our EOL policy (that right now isn't clear, not even between us).

This PR is a proposal that we agreed upon with them, and should help us keep the current low overhead maintenance of previous releases. We can do this only if we continue to be able to move the ecosystem quickly with us, so investment in vite-ecosystem-ci will keep being crucial.

If we merge this PR, we will announce in the Vite social accounts that Vite 2 will be in EOL once we release the next Vite minor to put a date from when we enforce the automatic EOL we are now declaring.

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[bluwy]

Patak would you like to update this PR still?

[patak-dev]

@bluwy I updated the PR to avoid the use of EOL. Let me know if the new wording makes sense to you.

About having a graph like Node has for EOL, I think that is more useful to know future dates as they are fixed in Node. Maybe could keep updating the "As an example" section for now everytime we do a release so we have the current range there. Or we could play with a graph in another PR if someone has a good idea for it.