Improve documentation for authorization

### Description

The documentation on authorization is very technical and appear to assume prior knowledge on the subject. I suggest updating it to make it more approachable, see below.

### Additional Information

I suggest the following updates:

**[Definere autorisasjonspolicy](https://docs.altinn.studio/nb/app/development/configuration/authorization/)**
- Explain where and how to configure authorization rules in Studio Designer
- Explain the examples - what is changed and what is the result (in plain words).
- Explain PEP

**[Regelbibliotek](https://docs.altinn.studio/nb/app/development/configuration/authorization/rules/)**
- Try and explain the rules in a less technical language and include concrete examples.
- Explain tags and roles (or link to explanations)
- ORG and APP: exactly which info in applicationmetadata.json replace these fields?
- RULE_ID: how should this be configured?
- REGNA: what is this?
- Explain Task1
- Explain in detail how to add a new rule
- e.g. for confirmation step
- Include which file to update (and its location), which piece of code to add and where, what needs to be updated in the code and how.

Start with the linked Definere autorisasjonspolicy and Regelbibliotek pages, then inspect the referenced applicationmetadata.json fields and existing examples. Done means both pages explain configuration, PEP, tags, roles, rule creation, and concrete outcomes in approachable language, including the requested confirmation-step guidance.

Written by the indexing model from the issue text.