Review Readme

The current readme can be updated to make it more biginner friendly and easier to follow code:
- Add source code of project to allow people to run the project and to refer to the parts of code mentioned in the Readme, see #12
- Remove the MOOR section, see also #15
- [ ] Read the persistence documentation: https://flutter.dev/docs/cookbook/persistence/sqlite
- [x] Read the state management documentation: https://flutter.dev/docs/development/data-and-backend/state-mgmt
- Research widgets that can be used instead of creating custom ones: https://flutter.dev/docs/reference/widgets
- Add tests to the project to make sure the todolist is working properly

The flutter documentation contains all the information that we need to know how to create the todolist. However it can take a bit of time to test everything. I'll write a recap of the section we are using on this project.
The [cookbook section](https://flutter.dev/docs/cookbook) contains some code example which can also help us to create the todolist