Ci build

[Riscky]

This is WIP, but the idea is to build the website in CI, then upload the build to S3 and trigger a deploy. This is one of the components of svsticky/sadserver/issues/327

The current build pipeline does everything except triggering the deploy, which will require some changes in sadserver and aas I also updated npm to the lastest version (nvm install --latest-npm), which fixes a bug in the build, but requires updating Netlify and local environments.

TODO:

• [x] More caching (at least .nvm)
• [x] Use the right triggers (master + PRs)
• [x] Make the workflow trigger on a webhook
• [x] Fix current errors
• [x] Figure out what to do with the master/development paradigm (tags?)
• [ ] Trigger an actual deploy
• [ ] Try to do something about hardcoded npm paths
• [ ] Alerting when something goes wrong
• [ ] Make Netlify happy again (Netlify is using an outdated npm version) (see https://docs.netlify.com/configure-builds/manage-dependencies/#npm)
• [ ] Add instructions to the readme for updating local npm
• [ ] Autosquash and merge

[Riscky]

closing this because I made a wrong assumption. Going back to #300