Setup volta

[NullVoxPopuli]

This'll need thorough testing, because the volta action is meant to replace setup-node.

But:

• Support pnpm cache volta-cli/action#121
• Use @action/cache to cache where possible volta-cli/action#27

The volta action may not have sufficient caching for workflows trying to be most optimized.

To test this action out, replace:

-- uses: NullVoxPopuli/action-setup-pnpm@v2
+- uses: NullVoxPopuli/action-setup-pnpm@NullVoxPopuli-patch-1

In neovim, do it all in one go with a : command

%s/action-setup-pnpm@\(.*\)/action-setup-pnpm@NullVoxPopuli-patch-1/g

and to revert

%s/action-setup-pnpm@\(.*\)/action-setup-pnpm@v2/g

[NullVoxPopuli]

Gonna declare using volta at all blocked by needing them to implement a cache so we don't lose the cache with the existing setup.