Adding some information of documenation structure

1. Perform the development of functionality on capif code respository.

2. Create an issue on [Documentation Gitlab](https://labs.etsi.org/rep/ocf/documentation/-/issues)

3. Create new branch with source from **develop**.

4. Update documentation. ***Remember to update index.md with new functionalities for latest version***

4. Update documentation:

   1. ***Remember to update index.md with new functionalities for latest version***

   2. New testplan is defined? **Update test plan documentation**

5. Check if all new documentation is ok using **mike** [Checking documentation with local deployment](#checking-documentation-with-local-deployment) section.

6. Push changes to branch.

7. Create Merge Request.

  - FAQ: ./FAQ.md

```

As you can see we have 4 main sections:

* Overview:

  * Here we must place high level information like, version changelog, some inital scripts, ...

* Getting Started:

  * This section must contain a simple way to start working with project.

* Testing:

  * Detailed information of **how to test** OpenCAPIF, and test plan developed to ensure the code has all implemented functionallity checked.

* FAQ

## Main page

The page shown on firt view is at doc/index.md.

The page shown on first view is at **doc/index.md**

That page should be updated with latest changes on CAPIF, also including the version.