Incorrect or outdated CONTRIBUTING.md guidelines

**Describe the bug**
Incorrect or outdated documentation on how to contribute to this project.

**To Reproduce**
[The contribution guidelines](./CONTRIBUTING.md) state:

```
In development, go in examples/example1 and run npm start to build (and watch) the project source, and run the [development server](http://localhost:8080/).
```

However, that directory does not exist.
