Add screenshot to documentation

README.rst

@@ -2,23 +2,21 @@
 Graph Exploring Tool
 ####################
 
+.. image:: docs/ui.png
+   :alt: Screnshot of the user interface
+
 Installation
 ------------
 
-.. code-block:: shell
+..
+   .. code-block:: shell
 
-   sudo apt-get install libglfw3
-   sudo apt-get install libglfw3-dev
-   sudo apt-get install freeglut3-dev
-   pip install graph-exploring-tool
+      pip install graph-exploring-tool
 
-or
+   or
 
 .. code-block:: shell
 
-   sudo apt-get install libglfw3
-   sudo apt-get install libglfw3-dev
-   sudo apt-get install freeglut3-dev
    pip install --index-url https://pip:glpat-m8mNfhxZAUnWvy7rLS1x@git.rys.one/api/v4/projects/264/packages/pypi/simple --no-deps graph-exploring-tool