CI: Fix pnpm build

[Septias]

I'm using pnpm in the project, but the action does not currently support package.jsons which are not in the root folder. See here for reference.
Solutions:

• Use nxp in the subscripts to be independet of package manager.
• Switch project to npm.

Npm is kinda outdated these days so I would not like to go back to npm. If neccessary we can do that though.

[link2xt]

I have fixed the tests in #19 by using npx pnpm in CI and merged it once CI passed.

Regarding this issue, I would prefer using npm. It is preinstalled on GitHub Actions ubuntu runner, it is packaged in major Linux distributions (unlike pnpm), every JavaScript developer knows how to use it and almost every npmjs.com package is tested with npm. For large projects there may be some benefits of using pnpm, but we are not even using it for DC desktop, and for installing and running vite to build small .xdcs it seems to be an overkill.

[Septias]

Well in the end pnpm is just npm with some performance benefits. Every basic command you run is the equivalent to npm so everyone who knows npm can work with pnpm easily. If you don't want to install pnpm, you can always just use npm instead (which will not use the package.lock but should build fine aswell) and there is an easy fix for the build problem (#19). As I use it everywhere (I have a lot of js projects where shared dependencies is very nice) I would like to use it here aswell but if you think npm is better, we can do that aswell.

[link2xt]

I guess it's fine, the build works for everyone who has npm installed by using npx pnpm.