ci: use pnpm

[rubiin]

Updates the ci to use pnpm.
Also drops end of life nodejs versions which are too old

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)

[WikiRik]

Any reason why pnpm instead of npm (or yarn)?

Also; this is a breaking change so we'll need to do a major release for this

[rubiin]

pnpm because its like a superset of npm . Most commands are similar .Also I use pnpm comparatively more.
I bet anyone would be using the node 16 and below, most libraries already dropped support for them. Supporting them would mean we have to use tools like babel to transform latest js features for older runtimes
But we will have to do a major release considering it might be a breaking change

[rubiin]

closing this for now , will revisit later