docs: improve README (#54)

Closes #19.

### Summary of Changes

See the issue for more details.

docs/README.md

@@ -5,7 +5,19 @@
 [![codecov](https://codecov.io/gh/Safe-DS/Stdlib/branch/main/graph/badge.svg?token=HVRP1633B1)](https://codecov.io/gh/Safe-DS/Stdlib)
 [![Documentation Status](https://readthedocs.org/projects/safe-ds-stdlib/badge/?version=latest)](https://stdlib.safe-ds.com)
 
-A user-friendly library for Data Science in Python.
+A user-friendly library for Data Science (DS) in Python.
+
+Our goal is to make DS more accessible to a wider audience by providing a simple, intuitive, and consistent API to solve common tasks on small to moderately sized datasets. As such, a major focus is to provide a learning tool for DS novices.
+
+Instead of implementing DS methods from scratch, we use established DS libraries under the hood such as:
+
+* [pandas](https://pandas.pydata.org) for data manipulation,
+* [scikit-learn](https://scikit-learn.org) for machine learning, and
+* [seaborn](https://seaborn.pydata.org) for visualization.
+
+ For more specialized tasks, we recommend using these or other DS libraries directly.
+
+Note that this library is still in development and not yet ready for production. Expect breaking changes in the future without a major version bump (while in the `0.x.y` version range). Feedback is very welcome! If you have a suggestion or find a bug, please [open an issue](https://github.com/Safe-DS/Stdlib/issues/new/choose). If you have a question, please [use our discussion forum](https://github.com/orgs/Safe-DS/discussions).
 
 ## Documentation