Add tutorials that walk though different Macaron use cases

[nathanwn]

We are planning to add some tutorials for Macaron that demonstrate some main use cases of Macaron. These tutorials will mainly target new users.

In these tutorials, we can, for example, walk new users through how to:

• analyze a specific repository
• compose some expectations in Cuelang
• compose some policies in Souffle Datalog
• interpret the results

[behnazh-w]

I will keep this issue open to add a few more tutorials.