The page on Process Handling is a stub that needs updating

The current page on [ProcessHandling](https://docs.altinn.studio/teknologi/altinnstudio/solutions/altinn-apps/app/processhandling/) needs be be looked at and improved. There are some documentation on [altinn.github.io/docs](https://altinn.github.io/docs/altinn-studio/app-creation/prosess/) as well, so a solution might be to link to that.

Open the ProcessHandling page and compare it with the related content on altinn.github.io/docs. Determine whether the page should be expanded or link to that documentation; it is done when the stub has useful, current content or a clear link to the relevant guidance.

Written by the indexing model from the issue text.