added Agenda component and related items

[anbrue]

Description / Motivation

The Agenda component is added with PR, it is functional, not ready. It needs styling.
Also there is a FE-specific comment for the FE Devs in the team, it's about the hook.
I used the useSWR hook for fetching the data, because it is highly recommend to use that rather than the useEffect hook.
The old approach works with getStaticProps, but the problem with that is, that the data are fetched on build and especially for the agenda we need to have a recent version in place, because the agenda needs to be update in Sessionize during the event.

Let's discuss please the pros and cons of this, this is just my suggestion.

How Has This Been Tested?

Tested it locally, works in my FE app and in Pages connected to my local CM.

Types of changes

Added the component and related items.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have read the Contributing guide.
• My code/comments/docs fully adhere to the Code of Conduct.
• My change is a code change.
• My change is a documentation change and there are NO other updates required.