Activate venv in current terminal

CONTRIBUTING.rst

@@ -79,15 +79,16 @@ a `devcontainer`_ that installs required dependencies for you.
 -   Fork Flask to your GitHub account by clicking the `Fork`_ button.
 -   From your fork's repository page, click the green "Code" button and
     then "Create codespace on main".
--   Wait for the codespace to load and the "postCreateCommand" to
+-   Wait for the codespace to load and the ``postCreateCommand`` to
     finish running.
--   Open a new terminal or run ``. .venv/bin/activate`` to activate the
+-   Open a new terminal or run the following command to activate the
     python virtualenv.
--   Checkout a new branch and `start coding`_.
 
-Note that when you reconnect to an existing codespace, you may need to
-reactivate your python virtualenv by opening a new terminal or running
-the ``. .venv/bin/activate`` command.
+    .. code-block:: text
+
+        $ . .venv/bin/activate
+
+-   Checkout a new branch and `start coding`_.
 
 .. _GitHub Codespaces: https://docs.github.com/en/codespaces
 .. _devcontainer: https://docs.github.com/en/codespaces/setting-up-your-project-for-codespaces/adding-a-dev-container-configuration/introduction-to-dev-containers