Readme: formatting fixes

Author: gsmolk

README.rst

@@ -21,6 +21,7 @@ Installation
 DEB packages for Debian|Ubuntu:
 
 .. code-block:: bash
+
     echo "deb [arch=amd64] https://repo.postgrespro.ru/mamonsu/latest/deb/ $(lsb_release -cs) main-$(lsb_release -cs)" > /etc/apt/sources.list.d/mamonsu.list
     wget -O - https://repo.postgrespro.ru/mamonsu/keys/GPG-KEY-MAMONSU | sudo apt-key add - && sudo apt-get update
     sudo apt-get install mamonsu