Organized setup instructions (#115)

* Organized setup instructions

* update tets

* link checker action

* raise error upon broken link

* fix links

* fix links

* delete duplicated paragraph

setup/02_installing-python-libraries/tests.py

@@ -0,0 +1,14 @@
+# Copyright (c) Sebastian Raschka under Apache License 2.0 (see LICENSE.txt).
+# Source for "Build a Large Language Model From Scratch"
+#   - https://www.manning.com/books/build-a-large-language-model-from-scratch
+# Code: https://github.com/rasbt/LLMs-from-scratch
+
+# File for internal use (unit tests)
+
+from python_environment_check import main
+
+
+def test_main(capsys):
+    main()
+    captured = capsys.readouterr()
+    assert "FAIL" not in captured.out