[Documentation] Add some architectural views in the project

[Madunguin]

**Is your feature request related to a problem? Please describe. My team and I believe that adding some architectural views will help new developers collaborate on the project or use the program more easily.

Describe the solution you'd like We think that adding then in the Read Me will help then.

Additional context We are a group of students and in our project we had to investigate what is eXist-db, and we think really think that with these diagrams more people will understand how eXist works .