Add README to presentations folder

[e-backmark-ericsson]

Description

There should be a README.md in the presentations folder with a general description on what is stored there, along with a link to the Youtube channel stating that some of the presentations are available in video format in that channel

Motivation

Easier access to recorded material and basic info about what the presentations are about

Exemplification

https://www.youtube.com/@EiffelCommunity

Benefits

Obvious

Possible Drawbacks

None