Add app README inside sample_editor/

Moves the original Sample Text Editor README (run instructions, author,
GPL icon license) next to app.py, where its relative paths resolve.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: realpython-bot

qt-designer-python/sample_editor/README.md

@@ -0,0 +1,29 @@
+# Sample Text Editor
+
+A **sample text editor** that shows how to use Qt Designer to create GUI applications.
+
+## How to Run this Application
+
+To run this application, you need to [install `PyQt6`](https://realpython.com/python-pyqt-gui-calculator/#installing-pyqt) on your Python environment. To do that, you can run the following commands in a terminal or command prompt:
+
+```sh
+$ python3 -m venv ./venv
+$ source venv/bin/activate
+(venv) $ pip install PyQt6
+```
+
+Once you have [PyQt](https://www.riverbankcomputing.com/static/Docs/PyQt6/) installed, you can run the application by executing the following command:
+
+```sh
+(venv) $ python app.py
+```
+
+This command will launch the application, so you'll be able to experiment with it.
+
+## About the Author
+
+Leodanis Pozo Ramos – [@lpozo78](https://twitter.com/lpozo78) – lpozor78@gmail.com
+
+## License
+
+The set of icons used in this application are part of the [TurkinOS](https://github.com/llamaret/turkinos-icon) icon theme, which is distributed under the [GPL v3.0 license](https://github.com/llamaret/turkinos-icon/blob/master/LICENSE). See `ui/resources/LICENSE` for details.