Update "Getting Started" section

[coloradomorrissey]

Originally posted in Slack by @rmfaheem

I think the "getting started" section is not working as intended. I think it may actually be working as an entry barrier to ESDB.

People may read about our product description on our website and think "cool, let me try this". They go to our docs and, obviously start with the "getting started" section and then they are greeted with this wall of text which is mostly links to other parts of the docs or external material. The external references themselves which when put together amount to several hours worth of material to consume. This could be discouraging new, unfamiliar users from trying our product.

I think we should put those external references in a different section of the docs and instead explain the basic concepts of EventStoreDb, such as streams and events. Then we show them how to start the database and access the Admin UI.