update overview doc

Author: vgvoleg

docs/conf.py

@@ -44,6 +44,7 @@
     'sphinx.ext.todo',
     'sphinx.ext.napoleon',
     'sphinx.ext.coverage',
+    'sphinx_copybutton',
 ]
 
 # Add any paths that contain templates here, relative to this directory.

docs/overview.rst

@@ -14,25 +14,25 @@ Prerequisites
 -------------
 
 * Python 3.8 or higher;
-* `pip` version 9.0.1 or higher;
+* ``pip`` version 9.0.1 or higher;
 
-If necessary, upgrade your version of `pip`::
+If necessary, upgrade your version of ``pip``::
 
-    $ python -m pip install --upgrade pip
+    python -m pip install --upgrade pip
 
 If you cannot upgrade `pip` due to a system-owned installation, you can run the example in a virtualenv::
 
-    $ python -m pip install virtualenv
-    $ virtualenv venv
-    $ source venv/bin/activate
-    $ python -m pip install --upgrade pip
+    python -m pip install virtualenv
+    virtualenv venv
+    source venv/bin/activate
+    python -m pip install --upgrade pip
 
 Installation via Pypi
 ---------------------
 
 To install YDB Python SDK through Pypi execute the following command::
-    
-    $ pip install ydb
+
+    pip install ydb
 
 Community
 =========

docs/requirements.txt

@@ -1 +1,2 @@
-sphinx_rtd_theme==2.0.0
+sphinx_rtd_theme==2.0.0
+sphinx-copybutton==0.5.2